How about, when a house is relinquished and bought both players in question have thier gil transactions for the past X amount of time looked into. If a large amount is transferred from the new owner to the old owner by any means then both accounts are temp banned, new owner loses the house, and old owner loses all the new gil. In other words. the GMs could ACTUALLY do their jobs by upholding the ToS and there is a gil sink that is worth a damn.