Second homes tend to be in vacation locations, not where people are trying to buy their primary residence.

People aren't buying two homes in the same city alternate between them while keeping young homeowners out.

Yes they are. I know such people. Usually the second/third/fourth homes get rented out as AirBnBs.

Exactly, and what’s the occupancy rate for those Airbnb? 80%, 50% 20%? I knew one family that could make more an Airbnb in a week than they could renting it for two months.

We are incentivized by our greed nothing else.

Perhaps, but so what? Acting morally superior doesn't fix that. You don't change people's habits or desires. You either change the incentives (good luck with that in this particular case), or you... build more housing and make it not a problem that people own multiple homes.

Shame used to work wonders to get people to change their behavior. It’s still does. That’s the thing about morals, included with it is shame.

Good luck with counting on people to have shame and a moral compass (esp the wealthy). There's a ton of bigots on X (Twitter) who just love beating their chest showing they're a bigger biggot than the next. It's the generation of F* you, I've got mine, and not all of us are like that, but too many definitely are.

>It's the generation of F* you, I've got mine

Which generation exactly?

All of them.

AirBnBs are hotels. Perhaps they should be regulated as such?

Anecdotally, of the many people I know who own second homes, ~80% or more are not rented out when the owner is not there. In at least half of the cases Airbnb is expressed prohibited by their community/municipality

> Second homes tend to be in vacation locations

> AirBnBs

It's unfortunate that sometimes vacation destinations also can be places where lots of people want to live but the PP was not wrong.

I stand to inherit from such people. They own five homes, are building a sixth, and have plans for 1-2 more at least. 4 are rentals, 1 is a charity to my Uncle who is mentally unwell and unable to provide his own living. They don't think they have that much money.

It's all relative, but supposedly the top 1% had $11M in the US in 2022 (e.g., via https://www.forbes.com/advisor/investing/financial-advisor/a...). That means, 5 averagely priced houses do not put you in the top 1%, however, 1 big mansion in a nice area could.

$11M is net worth, not all of which needs to be held in residential real estate. I would expect a lot of people in that ballpark of net worth to probably "only" have a few million sunk into real property. The rest would likely be in securities.

Also consider that someone with 5 houses may not even have all that much of their net worth in the houses; the could largely be financed.

Untrue - it often takes the form of: somebody bought a townhome in the city 20 years ago, they use the appreciation to buy a house in the suburbs, they move and keep the city home and rent it out.

> Untrue - it often takes the form of, somebody bought a townhome in the city 20 years ago, they use the appreciation to buy a house in the suburbs, they move and keep the city home and rent it out.

Renting a home out is still productive.

Keeping it empty is not. I was pointing out that people aren't buying two homes in the same city to keep one empty.

Renting a home out is not productive. It’s financial capitalism. Is rentier capitalism. There’s no product being made.

It's a reasonable thing to predict quanatatively. If second homeownership was not legally possible, how much would it affect home ownership rates? (given all other things equal)

Just about every vacation destination in the world is a place where other people are trying to live. Pretending otherwise is bizarre.

Eh.. there are housing shortages in almost every one of the locations where people buy second homes too. All of the ski towns, all of the beach towns, tons of Southern warm-climate cities like Sedona and Las Cruces.

That is exactly what’s happening in many places. A new condo development went up near me, and over 80% of units were immediately purchased by investors. Not giant corporations, but local individuals buying for mainly AirBnB use.

No one is so special they should soak up resources on “second homes”.

Sorry capitalism, but you’re just a hallucination of less civilized and less educated, long dead meat suits

Gen Alpha is graduating high school, running into the same issues as millennials and Genz

If you all think 200 million-ish are going to coddle the dyings social norms, this forums audience isn’t as intelligent as the reputation might suggest

Knowledge != Wisdom

Philosophy != physics

The aggregate will bin philosophy for direct confrontation if philosophy manufacturers too many vacuous excuses that over burden biology

I think you're right on, but this position is deeply unpopular with the people that own those additional homes. It should also be said that, anecdotally, the same people that own a bunch of homes as "investment properties" are also the most likely to be NIMBYs because their wealth is tied up in real estate property values.

So... we have a housing shortage.

I try (and sometimes fail, but I try) not to judge people for what they choose to spend their money on. Wealth inequality is a thing, to be sure, and we can argue that perhaps there just should not be that many people who can afford 2 (or 3 or 4) homes. But that aside...

If people want to buy more houses, that's fine. If there are people who can't find an affordable home, that means we have a shortage, and building more will tend to alleviate that problem.

There is truth to this. 3/3 interns of mine whose parents live in the Bay Area have # of homes in the neighborhood > # of adults occupying them.

> It’s just greed.

These people whom I know personally, they are not greedy. They're not even selfish. They're not the bad guys.

Why don't the rich rent their vacant homes to the poor? At least we can answer this question objectively: if you're poor, you have less to spend, you can't fix your stuff, you will have more occupants, you will pay late more frequently, you will not be able to pay rent increases, you will not be able to adapt to extraordinary events like fires and layoffs, you have higher legal risks like tenant lawsuits, you will...

The crazy thing is, in every sector, sellers are less interested in poor buyers.

If you have more than you need while others are suffering it’s greed. You can’t change the definition of greed just because it makes you uncomfortable.

What if we made it a law that no one could own a second home before everyone owned a first home?

Not to nitpick, but the common definition of greed is different:

> Greed is an insatiable desire for material gain (be it food, money, land, or animate/inanimate possessions) or social value, such as status, or power.

Keyword: Insatiable. Lots of the people in the Bay Area are simply looking for a secure future for their children. Why is this unreasonable?

Edit: Thanks Podgajski, I like your definition below better.

I found a less extreme definition:

intense and selfish desire for something, especially wealth, power, or food.

Just about every single Westerner has more than they need in some way, and there’s plenty of folks suffering in the world. Your definition uselessly labels everyone greedy and also does nothing to help those that are suffering.

It’s not the job of individuals to fix our global economic system by changing their individual (legal) behavior. This is a regulatory problem.

I’m not useless at labeling people, greedy, I’m usefully, labeling, greedy, and I agree, we are exploiting most of the world because of our greed. We should all come to face that, and not only our live will be better, but the whole world lives will be better. And it would probably stop climate change as well. This is a regular problem that we can change with first our behavior as living by an example. This is why I don’t feel so bad, being homeless and living with less.

You literally can’t change this solely by changing your own first order behavior. Only by higher order approaches can you achieve change. (Saying stuff on the internet is not one of those approaches. Being homeless isn’t either).

It's not greed. You cannot blame people for taking what's incentivized and in front of them.

One resource America has is a lot of space and we had many generations of easy money and government policy that encouraged such behavior.

That's... still greed. It's just not a big deal to be greedy, because we all kinda are. We all have negative traits to some degree though.

If there’s four slices of pizza in front of you and there’s a person sitting across from you, you’d be incentivized to take all four of the slices. Doing so would be greedy. Not being greedy is making sure the other person gets what they need before you take the rest.

I can surely blame people for taking what’s in front of them when people who are also in front of them have nothing.

Stop with this fake morality.

When young people get hold of a home, then later sell it, none of them will be giving a "social" discount on the price.

Private property is private.

I can assure you my morality is 100% legitimate.

I believe for instance that property is theft, as Prodhoun proclaimed.

The fact that we see housing as an investment is part, no, probably most of the problem.

I frankly just cannot this seriously. And I think the vast vast majority of people in the world would find Prodhoun's view of property to be laughably unworkable, or at best just undesirable.

I do not believe people whom say property is theft as it would mean I can randomly take your personal items as they're not your property, since you don't believe in the concept.

But should you genuinely believe that and walk the talk, fair enough. I'm more of a pragmatist myself.

You would have to read Proudhoun an Anarchism to understand what is meant by the saying.

By "property", Proudhon referred to a concept regarding land property that originated in Roman law: the sovereign right of property, the right of the proprietor to do with his property as he pleases, "to use and [to] abuse," so long as in the end he submits to state-sanctioned title. Proudhon contrasts the supposed right of property with the rights (which he considered valid) of liberty, equality, and security. Proudhon was clear that his opposition to property did not extend to exclusive possession of labor-made wealth.

Private property is a construct of the state, which is itself either just fenced goods stolen from the powerless or the commons.

It's a social norm we maintain, with some limitations, because it's useful. It's not sacred.

At the time all of these people purchased their (absurdly cheap, relatively -- or tax/interest-incentivized) second houses, there was nobody sitting across from them.

That's what you fail to understand.

I’m the OP, and I definitely understand. Maybe that would be a good idea, once someone goes to apply for a mortgage there has to be a homeless family in the office right next to them.

Other peoples' buying activity is not the reason you're homeless.

/someone who has been homeless and has also bought a home.

For sure it’s not the only reason, but it’s a reason I can’t afford to rent anywhere since Covid for sure.

By the way, I’m homeless because I have a serious mental illness. Not all of us are equipped to jump back in the workforce.

I understand and sympathize. And I'm sorry to guess correctly that it would be mental illness. I still think there's some misplaced blame going on here.

I can’t blame myself. I am doing everything possible. I used to be able to afford a rental. I did nothing different. So where is the blame?

Sure, it's certainly greed. That people were (are) incentivized to be greedy doesn't mean it's not greed anymore.

Not at all. Greed requires selfishness.

If you're presented with abundance, everyone is taking a similar share and there isn't counterpressure from your peers (e.g., laws that we vote for), then there is no selfishness and thus no greed. To define greed you need a feedback loop.

We're simple dumb animals. We take what's available. If you want to talk about defining arbitrary limits on consumption that are disconnected from circumstances then you're basically out here preaching religion.

Taking more than you need when others are lacking is selfishness. Counterpressure doesn't enter into it. If the only thing that stops you from being greedy is that other people or laws pressure you to not be, then you're still a greedy person. Our values are expressed by what we do in the absence of such pressure.

In the scenario I just described no-one is lacking.

When boomers bought all of these second/vacation homes cheaply in the 80s it wasn't in places with huge demand from underhoused people.

These arguments need a little more consideration of facts rather than appeals to emotion.

I hate to say it, but there was homelessness in the 80s and it is only eclipse by our current state of homelessness.

https://www.coalitionforthehomeless.org/wp-content/uploads/2...

Not. Where. People. Bought. Second. Homes.

Nobody was buying second apartments in NYC in the 80s. Nobody was buying apartments period. I knew people with brownstones for sale in spanish harlem that they couldn't get $10k for in the late 80s. 80% of _storefront_ space in midtown was vacant.

People buying vacation homes in Florida or Vermont aren't responsible for homelessness in major cities.

It amazes me how people pick and choose when they want us to be “dumb animals“. And it amazes me that someone on hacker news would say this. Even dumb animals are more communal and fair than modern humans are.

I personally would feel a great deal of guilt if I purchased a second home in my city, knowing that there are thousands of people who would kill for the opportunity.

To me, it is indeed greed. Some things are more sacred than money and housing is one of those things

But outside of a few outlier markets like SanFran/Vancouver/NY, which are mostly being used to expatriate stolen foreign money anyway, that's not how the majority of people acquired a second home.

can you elaborate?

I suspect a great deal of people buy a second home while maintaining the first one as a rental, if they can swing it.

with all of the "free" money out there over the past few years, it was insanely easy to pull equity of your home to buy investment properties. I don't have numbers but I can't imagine this is a small amount.

Nobody's swinging that in high demand markets. A lot of dumb people _tried_ to leverage themselves and lost their ass on airbnbs that aren't performing (airbnb has seen huge decline).

The overwhelming majority of second homes are vacation homes. _Landlords_ aren't keeping people out of housing -- quite the opposite.

Home ownership is kind of an endless money pit anyway. Most people are better off renting in any of the markets we're talking about homeless populations anyway.

People are also extremely bad accountants, and if they sell a house for more than they bought it they accrue everything to profit, even if the rents during the time barely covered the mortgage (and/or didn’t cover repairs and maintenance at all). Large appreciation has hid the real costs associated with landlording.

landlording is really all about economies of scale to both the owner and renter's benefit.

Ideally landlords should be able to get better pricing for maintenance.

Unfortunately our dumb FREE MONEY monetary policy has absolutely wrecked the trades and saddled generations with bad debt chasing worthless credentials.

...YOU ARE PERFECT! https://www.youtube.com/watch?v=4p8vqoIVESc

I am sorry about your situation. I feel that simply building more houses is easier than trying to get the surplus houses out of the possession of the people who want several houses. As the fine article concluded, we are a rich country and we should act like it by building the appropriate number of houses.

I am sorry about your conclusion, but you're ignoring all the knock-on effects. These houses are utilizing prime locations and locations anywhere near the city centers where the majority of jobs are. They're sitting there empty for large portions of the year depriving the local economy of patrons. They're owned by wealthy individuals who are driving up the housing costs in the entire area, which also benefits them as the value of their 'investment' increases and the ability for the average person to own a home diminishes. "Just build more houses".... where? at what cost? Are you going to tell people to stop trying to buy houses where the jobs are, where the modern services and utilities are?

"We" are not a rich country, unless by "we" you mean the 10% of the population that is rich. I feel well compensated, I'm well within the middle class and consider myself lucky. I cannot afford a home, in the current market, in a location with the services and locality of my industry. I live in Florida. Vrbo, Airbnb, and properties purchased by institutional investors have directly increased my housing costs. That is objective, not subjective. Call it anecdotal all you want, the populated parts of the state have seen their housing options obliterated.

While we're on the topic, let's not forget foreign investors. Most of the properties in my neighborhood were purchased by foreign investors. My block in particular has at least 4 houses that are owned by asian investors. I've met the families who live-in and rent those houses. The property management company also runs the HOA and votes by proxy for those investors, investors who don't care about the daily goings-on of the community.

If we're going to use statistics for anything, let's look at it in the affirmative instead. How many homes are owned by the family living in them? The most recent data for Florida is for 2015-2019. Here are the owner-occupied housing for the most populated counties, starting with the one I live in.

Hillsborough County - 58.6% Miami-Dade County - 51.2% Orange County - 55.4% Broward County - 62.1% Palm Beach County - 68.9% Duval County - 56.7% Pinellas County - 67%

The National Average is 64.8%. In my county nearly half of the housing is not owner-occupied. As a nation, nearly a 3rd of available housing is not owner-occupied. I bet this is worse now, as this information is pre-pandemic and from the very beginning of the most recent housing rush.

https://www.census.gov/quickfacts/fact/note/US/HSG445222#:~:.... https://www.census.gov/quickfacts/fact/table/US/HSG445222 https://www.florida-demographics.com/counties_by_population https://www.census.gov/library/visualizations/interactive/ac...

Edit to add some relevant information: https://cdn.nar.realtor//sites/default/files/documents/2023-...

There is nothing ethically preferable about owner occupancy. In Switzerland, which I consider to be a highly developed society, they have a special tax that applies only to owner-occupants. I think we should adopt that. More people should rent, and fewer people should consider home ownership an investment strategy.

Also, to be quite honest, your allusions about shadowy Asians has the whiff of racist tendencies.

I'm sorry if there was any implication of bias against Asians as a group. I don't think I implied that at all, when did I call them shadowy? That smells of your own biases and perceptions. I was simply referencing the region of those I'm aware of. My neighbors home is owned by an investor from the Philippines. Three other houses on my block are owned by investors from China and are rental houses. This information can be confirmed by a simple property tax search.

I don't understand this stance. I want to own so I can customize to my liking. I want to own so I can add that solar system and battery backup. I want to own so I can add 2 ft of pavers on both sides of my drive-way. I want to own so that 30 years from now when I'm preparing to retire, that my only housing costs will be utilities and taxes. What person wants to never be able to call something their own?

Everyone who runs the World Economic Forum .

Building more houses might be easier, but it's incredibly difficult nonetheless, at least if we're talking about affordable housing. There is tons of housing being built in my area, but it's all for the wealthy. Literally nothing is being built for anyone who isn't rich.

And what affordable rental housing exists is increasingly being purchased by investment groups who then squeeze them for every dime, squeezing out the very people who need that housing in the process.

The housing crisis really looks to me like an aspect of the serious wealth inequality problem we have.

You add housing at the top of the market, the highest price point, because people will pay more for a newer home. Consequently the older ones become cheaper, because people who prefer the new ones and can afford them no longer compete in the market for older ones.

This has been dramatically demonstrated in Berkeley, where I live. We have added tons of 0- and 1-bedroom apartments recently. These are very expensive, $3000/mo+. This building boom has caused the price of rent-regulated older apartments to plunge. What had been renting for $2252/mo in November 2018 is now renting for $1688/mo in November 2023. That is a significant increase in affordability of studio and 1-bedroom apartment, effected by building newer, expensive ones.

Edited to add sources:

The discussion is too long for me to recapitulate here, but all of my data in various forms and some visualizations are available here:

https://observablehq.com/@jwb/berkeley-rent-board-data

Also in random tweets such as:

https://twitter.com/Jeffinatorator/status/172890293692602402...

I believe these are visible to non-account holders.

Can you please provide a source for the rent decreasing? Maybe a site showing the historical rental cost(s) for a given unit? I've not seen that happen in my market at all, I've only seen existing rental rates increase.

Edit: I think I see where a lot of our disconnect is coming from. We have no rent control here, rent very rarely decreases and is mostly pegged to comparative sq.ft. rentals in the area. Age of the property does not factor as much as location.

It’s also simple math. If 10k new units are built, you either need 10k new people to enter the market, or prices will drop.

Do enough of it and rents will begin to fall below loan maintenance, causing even more sales and more price drops.

Rent control only fights against upward pressure for existing renters... When you describe rents continually going up, it's due to more people competing for limited rental units. Cities can and do see rent declines (they first show up as "first month free" etc. before landlords bite the bullet and reduce rate). Seattle has seen temporary competition for rents in some neighborhoods as new construction started in 2019/2020 comes online. It won't last since we've seen such a decline in new construction starts, but the mechanism is sound.

But what's to stop wealthy people from buying the newly built houses as yet another asset to their real estate portfolio to the exclusion of first time homeowners?

If we remove the regulatory barriers to building more housing, the rich and the less rich can buy as much housing as they want.

Think about this in the context of any other good. No one worries that if we build more cars, they'll all be purchased by rich car collectors. Yes, when more cars are built, a few very rich people with many cars will buy more. But the increased supply also make it more economical for everyone to buy more cars.

Oh, yes. Nothing frustrates me more than seeing all these “luxury apartments“ being built everywhere. I never gave a crap about luxury. I just would like a stable, clean place to live. I even love studios more than a one bedroom apartment. But now even the studios are all “luxury“.

As I said, at other times in this thread, the only incentive we have as an and an economy in the United States, is agreed.

As I said, at other times in this thread, the only incentive we have in this economy and in the United States, is greed.

It doesn’t matter. The goal should be to build enough housing to make it a marginal investment, at which point it won’t be attractive to real estate investors. Of course, a house is still attractive to someone who wants to live in it.

Yes, this is exactly my point. The fundamental issue is greed, not housing. If we don’t get rid of the greed, these houses will be either bought up by investment corporations or the wealthy people that didn’t get second houses the first time around.

People will always be greedy. Theres nothing we can do to solve that problem. We can solve the housing shortage though. Investors wont buy homes when theyre easy to build because their value wont increase unless supply is constrained.

If we keep building housing, it ceases to become an interesting investment. That's what would stop them.

Do you not see the contradiction in your statement?

Houses are built by developers whom by definition only build a project when it's a sound investment. They immediately stop building when this isn't the case.

Different kinds of 'investment'. You're correct that if they can't turn a profit, they won't build. Same as with cars or bicycles or any other good. But that's not a long term thing - they want to sell the goods they have produced, turn their profit, and move on to the next project.

What people who buy homes are told, though, is to essentially 'buy and hold' because it's a "good investment" that will gain value over time, even if they are not building anything or adding any value to the dwelling they inhabit.

Where I live, during the recent runup in prices, the median home gained something like $100,000 of value in a year, which is significantly more than the median household income.

I'd say that most people do not buy a house for the investment. They actually live in it and any value appreciation is a side-effect. A pleasant one, but not the primary goal of the purchase.

Here's a chart of homeowner gains vs developer profits. It's a bit apples to oranges, but it gives you an idea of the scale of who benefits (at least on paper) from the housing crisis:

https://oregoneconomicanalysis.com/2021/03/16/who-benefits-f...

Ideally, I think, home prices would be fairly stable - neither appreciating a lot, nor dropping in value. Boring. That would also make them a 'bad' investment for corporations looking to make a buck by buying and holding.

> What people who buy homes are told, though, is to essentially 'buy and hold' because it's a "good investment" that will gain value over time, even if they are not building anything or adding any value to the dwelling they inhabit.

Do you expect people to buy and sell their home? It’s their home, why would selling (in the short term measured in decades) be the goal?

People primarily buy homes to live in. Any benefits of price appreciation, and/or political interests of those nearing their end of life and want to downsize/die are secondary.

In a perfect world, I would agree. But in reality that will never happen, and young people continue to suffer in the meantime. Housing should have never been allowed to become an investment.

There was a large drop in the price of housing just 15 years ago. Granted, other factors were involved, but that's part of what the article is about. It is possible.

This is that heart to what the problem is. Instead of letting the housing market, collapse and state collapsed the federal reserve started printing money nonstop to inflate assets, including housing. And they haven’t stopped since then. This is what causes separation of wealth in the United States, and the increase in homelessness.

And now the Fed can’t even get the guts to lower inflation by raising interest rates because of what it’s done to the housing market.

When I go to city council meetings to support housing, the problem is NIMBYs. Not macroeconomic conditions, but ordinary people who show up at an evening meeting to complain about - I kid you not - some code removing a number for garage heights. They wanted to use this to block some apartments in their neighborhood.

This kind of thing happens over and over and over again, all across the US and it adds up.

I don't live in your city but in my city we just got finished pushing a project approval through a 7-year political process. The project will build 1000 new apartments on the parking lot of an existing subway station. Most of the new apartments will be deed-restricted affordable housing. At the most recent and final hearing there were still Boomers showing up to demand the project be scrapped because they prefer free parking.

I hope you can keep building land, specifically land nearby a lot of employers and services, in order to build those houses upon.

We do have the technology to stack dwellings vertically, which is a good way to use scarce land more efficiently.

The problem is that it's not legal in most parts of most cities.

I am a YIMBY and still understand that these forms of housing are nowhere near as valuable as the SFH.

Just stating that Americans love their yards/privacy and it's not so simple to fix.

> I am a YIMBY and still understand that these forms of housing are nowhere near as valuable as the SFH.

Well, ok then - we want affordable housing, let's build affordable housing. Nothing's perfect. Some people prefer denser housing in a more desirable place, and some prefer more space in Cyanide Springs, Oklahoma. Both should be a choice, but currently, we limit the denser housing options way too much.

Nothing at all. This is exactly what's been happening in my area for a long, long time.

First of all I do not care if people rent or buy homes. Under my economic policies when I become god-king of America, owning a house will be the worst investment anyone has ever heard of and people will run screaming from the small-time flipper game. I will Make Landlords Poor Again. Vote Jeffbee.

Secondly if a person owns a home and rents it to a second person, I'm fine with it.

They would only buy it they felt the return was higher than other investments

If the capital appreciation is zero, then it's just the rental income, which is offset against the cost of maintaining the property and the opportunity cost from the capital outlay on the property. That's not a major problem though, as the rental price won't be able to get too high as people will simply rent or buy elsewhere (as you've reduced the other barriers to building more property)

Of course you can get rid of the appreciation by simply taxing the land (which is the thing that mainly appreciates -- the building itself typically depreciates), and get most of the way there.

> It’s not that we don’t have enough housing

How do you know?

I would not be homeless if my sister let me live in her second house. That’s how I know.

I meant more: how do you know we're keeping up with building vs population increase, but so narrowly that some people having second homes that they don't rent out are making all the difference?

High net-worth individuals (as per the article) represent a small fraction of Americans (if you break a $1000000 you're in the top 5%). That they might own a second home makes no meaningful impact on the market, notwithstanding the fact that average people aren't even competing in the same range (multi-million dollar houses).

More housing starts means more affordable homes. We've seen what zoning reform has done for cities. We don't build enough.

Investors collectively do purchase a good amount of new housing starts (like 18%?) but that's also spurred by interest rates and confidence that demand will grow. It's neither here nor there, build more and houses become more affordable.

Small fraction of people but a huge fraction of wealth. Top 10% having 70% of the wealth, e.g.

If we make the (extremely crude) assumption that the capital expended on that 2nd home could be moved elsewhere, we could have built more housing in cities instead of building and maintaining that home.

[0]https://www.google.com/amp/s/www.statista.com/chart/amp/1963...

If you consider what actually deters construction/building rates, there's no reason to believe that capital "moved elsewhere" (appropriated by some abstract entity / people) would translate to more housing.

Supposing everyone had more money in their hands (all else remaining equal), that would just be reflected in the market. Houses would increase in cost. Now you're where you started.

Housing supply is just too inelastic in most US cities.

The owner of the prior home I rented owns 50+ rental properties in the county, has a 1M+ family vacation house in the adjoining county, and lives in California. Explain to me how that made "no meaningful impact" on the market? That's ONE individual. Her brother also owns a number of properties in the area.

Nice anecdote, but now you're conflating second homes with rental units. Supposing they did not own 50+ rental properties, someone would have to own them if they're to be available for rent. They don't get built for nothing. Why is rental availability framed as a negative? You seem to be making an allusion that average people would otherwise purchase apartment complexes. Supposing they want to buy and not rent, they'd look at condos, and the construction of a condo is not contingent on not constructing apartments. This is not zero sum. If you have a growing population, you have to build.

At any rate, the point is that qua "second homes", they represent a drop in the bucket compared to the overall market. Home ownership rate is around 63%, for a population of 334 million. The inelasticity of housing construction whilst demand is steadily climbing due to immigration has far more impact on average housing prices than cases of the ultra-wealthy constructing or purchasing a mansion upstate.

If we make the assumption that each mansion housing a millionaire could be rebuild to a multi family home housing 10 people (or families), then those 5% houses become homes for 50% of Americans.

Consider what constitutes a "multi-family home" in the loosest sense and you'll find that zoning/regulation is what is prohibiting its construction. Otherwise, if there is demand, it will be built. 10 people will not buy a multi-million dollar mansion together, but they would buy a piece (or rent) of medium-density housing.

Those mansions also tend to be built far away from city cores, with large lots to maintain (with paid labor), more taxes to be spent for infrastructure cost, requiring a vehicle, etc. It would still be too expensive and unhelpful for average people.

WE don't build enough. Look at what zoning reform has done for Minneapolis.

> individuals

It's not the individuals owning the houses. It's corporations.

It’s both. Tens of thousands of units are owned by individuals looking to cash in on Airbnb in any given city.