It's already regulated, mostly at the city/town level, and every city zoning board gets lots of comments that "we do NOT need more trailer parks/apartment build

It's already regulated, mostly at the city/town level, and every city zoning board gets lots of comments that "we do NOT need more trailer parks/apartment buildings/'those people' in our town". Supply needs to be deregulated, though it might not be a bad idea to crack down on some of the excesses of slumlords as well.