Or default on the mortgage.

You’re not proving housing, you’re preventing people from having housing unless they pay you. When housing wasn’t a speculative investment it was far cheaper and far fewer people were forced to rent to make someone else money for no labour.

So you've never heard of duplexes? Default -> homeless

Some landlords rent out a room in their own house they live in. If they stopped renting there would be no additional housing available.

Couldn’t those that are currently such landlords have been incentivised to purchase smaller homes, making more large ones available? Or alternatively, some large homes could be subdivided.

Why should tenants pay for the greed of landlords? They get paid for doing nothing, the least they could do is bear their own risks.

Ok, but how do we handle this until we completely remake the world in precisely the way that lucian1900 thinks it should be?

I’m just pointing out that landlords are exploiting tenants and other arrangements are possible and have existed.

Building social housing, removing incentives for buy-to-rent, taxing second homes and capping rents to a fraction of minimum wage are all measures that can be introduced gradually on the way to de-commodifying housing.

They may not have bought a smaller house. Sometimes people buy a larger house because they have kids. When their kids move out they may rent out the rooms. While moving to a smaller place may make good financial sense in some ways, some people don't like to move. They like their neighborhood and house and all.

You just sit on your computer programming or whatever you do. That is just getting paid for typing which is not real work. Maybe you should stop being greedy and just type for free.

A home that later becomes too big could be exchanged for one that is appropriately sized, so a larger family could have a home available. However you spin it, you can’t get away from the exploitation.

And don’t be disingenuous, I get paid for labour while landlords get paid for ownership.

What do you mean "exchanged"? Are you suggesting people should just trade a larger (and more expensive) house for a cheaper one? Why on earth would anybody want to do that? They may sell their house and buy a smaller one, but "exchange"? Based on this comment and others of yours it sounds like you don't believe people should own land.

I think everyone should have a decent home. Homes that are too big for their occupants are an inefficient use of a limited resource. I don’t think it’s fair that some would get paid for no labour because of this mid-allocation.