On my server, you would never ever make enough gil with gardening to be worth it if you buy multiple houses. So this always amazes me when I see more than 1 person buying a house because of that.

There should be pre-req on buying a house to be honest- character must be level 50, character (not account) must be x amount of days old. A server transfer can't buy a house until 7 days after transfer. Must complete a quest (?) To able to buy a personal house. The quest will be after Ultima easy.