Just short and quickly:
You are looking to have as less data as possible ( means not much houses and abandonned houses and stuff)
People (groups) would just build 1 house if you make it possible to determine for people who can enter their doors. There should be a maximum (like 4 players can be assigned to 1 door)
I am aware of that you have much more important things to do, but if you cross your heart you will know that this idea is good for players and of course for your server stability/integrity as well.