This isn't the only case though. If I go buy land in a rural area where a home previously burned down and I want to just take my existing trailer and hook it up

This isn't the only case though. If I go buy land in a rural area where a home previously burned down and I want to just take my existing trailer and hook it up to the septic and well (from the burned down house), I can't do that most places. It'd be fine to be strict about garbage disposal, etc. (I personally think there should be severe restrictions and penalties around septic stuff since that can pollute other people's wells), but if someone only has enough money for the land and not the house I don't see why we need to restrict people from living in the RV while saving for the house.