"But let's say your mother-in-law wants to live in a tiny house behind your home. Where zoning allows them, the tiny houses must be bolted to a foundation, significantly boosting costs. But in other areas, live-in tiny houses aren't permitted at all."

Really?  I know someone who has a rather large mother-in-law home in a back yard in the middle of Anchorage and it's just sitting on jack stands.  Apparently, enforcement isn't a big issue.