I don't think rent is a real option as the game lives on "You can take a break" and you only need to log in every 45 days to save your house. If you take a month break you may end up not having enough gil to pay rent in the 14-15 days of your return. Just restrict how many houses one can have per world/data center. I can see allowing a personal and an FC house but you shouldn't have much more need then that. Also with this change make housing account wide for people that do have a ton of alts on the same server and open up airship/submarine missions and gardening elsewhere as there would then be no reason to own a whole ward of shell FC's that could be argued aside from the players own ego.