Just a shot in the dark, but are there any apparent problems with capping the rent at like half the mortgage? Or like 80%? Then there would be financial incentive to keep the tenant happy, to keep working, and keep the property in working order.
Of course, this does not take into account properties without mortgage, or properties where the housing was paid in part with liquid cash.
It also doesn’t take into account rising property taxes, business tax, rising maintenance costs. I’m not arguing in favor of these dirty landlord companies that jack up the rent at every opportunity, however you’d have to control interest rates and the ridiculous home prices if you want to keep rents reasonable based on a percentage of mortgage costs.