I haven't read all the posts. But in case someone hasn't fixed it. Houses can't be sold. What you pay for is a player to relinquish their land/plot at an arranged time so you can be the first to buy it. So you pay player X gil. Then X gil again to server for the plot. Then X gil to NPC for permit.

With that said. I would think it's against ToS since you could be scammed. Get your gil taken and no plot relinquished. Or worse. Have someone buy the newly relinquished lot before you can.