I think developing an entire neighborhood of SFH is more expensive than developing a duplex or quad, which is what most upzoning would legalize.

A duplex or quadplex in a desirable area being upzoned is still going to be well outside the realm of what anyone but the “big boys” can reasonably afford to develop.

They’re going to turn it into rentals, and do their best to maximize rent for each unit.

End result is paying an obscene monthly rent for ever-shrinking square footage, while anyone being paid below a living wage sits in the 20+-year-long queue for employer-subsidizing “affordable” apartments.

It's more than what your typical person can do, maybe, but the cost of the loan to develop a duplex in SF is not as large as you are making it out to be. There could be plenty of entrants to that market.

You can avoid this with condominiums.

Higher density doesn't necessarily mean all rentals.

Past a certain level of density, the only thing you can realistically own is a condominium. The key differences between renting an apartment and buying a condo that I was able to identify seem to be that condos are more expensive, harder to get out of if you want to move, and not covered by the city's tenant bill of rights ordinance.

Rentals must on average cover the debt, taxes, and profit for the owner. The tennant pays monthly rent including all of the above and has nothing to show for it when the lease ends.

Condos at least build some equity that you can recover when you sell. Sure there are some risks and maintenance costs that renters don't "pay" but it's all included in the rent, over time.

With a rental, a single entity is responsible for maintenance, if you don't like it, you can move.

With a condo, several entities are jointly responsible. If you don't like it, you can sue.

I would rather deal with a landlord than a Surfside Tower like incident.

> Condos at least build some equity

That equity is only monthly payment - debt, taxes. So the real difference is that you can invest X in your property or X-owner's profit in the investment of your choice.

If you take loan, it is also leveraged investment with some tax benefits, and lower risk: you can file for foreclosure if underwater without need to pay out of debts.