hmm thats the hard part... its sort of like a saints row game, theres a deed infront of the house that you can buy the house, and maybe like car_menu it would say, (Example) 32nd on 3rd street, XXXXX amount of $.

Than you would have acess to all doors, and the deed would say you own this house, then maybe there is a - sell house to (active members shown):
Snackpack
Storm
Natayla

Then they give you the house and you give them the money. I think if you are willing to set it up it would be easiest to set up buying and selling as car_menu buying and selling.

Then when you went up to the door it would say, so and so owns this house. Then you have the ability to kick people out, lock whenever you want without paying for doors, etc.etc.

It would make a lot of people make more money on the server causing more activity, more fun- more players.