The Sims: Makin' Magic Cheats

First wait untill the mysterious man comes, then place him upstairs -delete the stairs as he goes downstairs and wach him place the next box down

Create a two story house, and ignore the bottom for now. Customize the top floor as you want it to be(walls, floors, doors, etc.), and add stairs of some sort to the bottom floor. Delete The walls on the bottom floor, and you now have a floating house.