[GTLS]

Its just like how you create Player Toys System. Land will be a Dynamic object, which player can buy. with each land, its area will be stored for boundaries, and if a player is inside that area and owns it, he can /build something there. OnPlayerEditDynamicObject, you can check if the saved position is inside the area or not. If not, dont save the object there else, save it. This is the rough idea how a land system works.