This is taken from the IDOC FAQ above. I'm going to eventually update all these and organize them a bit. But there is alot of info on this forum that needs to be included.
Anyway. Hope this helps you understand what happened.
'If your account DOES NOT own a house or plot already, you may place a plot (the first plot at least) in the regular fashion, you WILL get the confirmation gump AND you will be warned that you can not place another house for 7 days.
However, you CAN place another house (even in the same spot but not sure why you'd want to unless you are placing a larger one), within the 7 day time period IF YOU DEMOLISH THE FIRST AND WAIT 15 MINUTES. You MUST be actually logged onto UO on that account during the 15 minute wait for it to work (and NOT own another house or plot).
This ONLY works if you DEMOLISH the house/plot NOT IF YOU TRADE IT OR SELL IT TO SOMEONE ELSE!
I'm not sure why the wait time is 15 minutes and not some other time period, like one hour or even 7 days, but Technically, if you place a house/plot on an account that DOES NOT already own one, AND then DEMOLISH it (and are not traded another one by another account or added a house in any other fashion to the account), you Technically Do Not Own a House on that account any longer.
Of course accounts that DO NOT own houses/plots CAN place a house/plot.
The only issue is that YOU MUST WAIT 15 minutes while LOGGED ONTO UO with the account that DOES NOT own a home that you wish to place with repeatedly.'
So the player could place a small one. Demolish it. Wait the 15 minutes in game, then place again.
Viola!