Use the following trick if you want your average Sim to purchase a house that is above his or her means. First, start a family or load one, and find an empty lot. Move the Sim on that lot. Activate the motherlode code a few times, just to the point where you can buy the expensive house. Exit the lot, but save the game. Then, evict (move out) the family. Notice that your family is displayed at the "Choose Family" window. You can now buy any house desired.