Buyable House System

[Gunderak]

Basically what i would like to accomplish is about 50 houses on the gmap which players can write /buy housenumber and buy it. they can only own one at a time and what happens is once they buy it itl add a weapon named house editor with free furniature which il script later but for now how would i go by making a tenent system? and only you can enter the house but you can invite people to it too? i am clueless of where to start .