[yurishimo]

If their fixed costs are low, the tenant could be making more through investments after staying in the same house for 15 years.

Buying makes a ton of sense if you're going to live somewhere for a long time of course, but if you start out not sure and you have a nice landlord that doesn't take advantage of you with perpetual rent increases every year, then it can make sense to ride it out and invest your "inflated" income every year instead. By the time the tenant moves out, they have a nice portfolio to leverage for a new property and the landlord has gotten a decent return on their investment with a stable tenant.

In this scenario, it seems to me that main driver of disparity in our society is landlords' push to always increase rent even when the mortgage is being paid 2x or 3x over each month, just because it's allowed.

I'm not saying we need rent controls necessarily as a way to fix the problem, but that is one problem that rent control solves. Perhaps paired with some other scheme (3% max increase per year for first 5 years of renting, then capped at 1%?) we could find a more equitable way to account for inflation of repair costs while not screwing tenants with "forced" moves every few years when the rent becomes unaffordable.