Oversupply will take care of the downstream issues. They will cease to be good investments and become commodities. Rents will have to come down in a competitive market.
Oversupply will have to be on a regional level. A vacant house in a small town doesn't compensate for an occupied house in a city 100km away.
Zoning laws prevent this in the US/Canada in many places. Existing homeowners don't want to change. More houses means more crowding, higher traffic, construction noise, obstructed skylines, more pressure on schools, police etc. We can't accept that argument when weighed against homelessness or poverty anymore. Fuck their skylines, shelter is a basic necessity and it often has to be close to work, shopping, school etc. Living in the middle of nowhere is not an option.