1) New permission: "open."
If set to "yes," people can visit the house even if I am not there.
So in addition to "primary" there should be a submenu with the houses I have set to "open".
2) Make a house where the floorplan is somewhat customizable.
Allow us to alter the floorplan
Allow us to alter the condition of the walls, etc. (Repair ruined walls, repaint, etc). You could potentially charge materials for doing thins.