We should enforce this with the law. Right now, landlords raise rents anyway. I've never once heard of a landlord lowering the rent once they finish paying their mortgage, even though their expenses are now far lower.
Let me be the first then. I've been a landlord for a decade. I've paid back each and every one of my tenants the rent I collected in surplus to costs. Adjusted upwards to reflect the appreciation of the unit.
I now rent at cost, choosing to believe that it's better to help the people who live with me establish themselves and build financial safety.
In some cases we have rented a mother in law unit. Are different apartments in the same building under the same roof?
I tend to be broader about community then many folks in the States. Imo, you live with the people in your local area, whether that's house, apartment building, or block.
I was inspired by someone else who did it and posted about it on Reddit somewhere a long time ago. So there are at least two, but likely many more than two of us out there.
Housing investment is a business. Buying the house is a risk, and you sink money and effort into it in the early phases, in the hope of getting profit out of it in the later phases.
If you are going to make that business unprofitable then no one will do it. People won't sign up for the risk, cost, effort and frustrations of being a landlord with no upside.
While we're on the topic, why not prevent programmers from putting their salary up? After all software is essential to society these days?