As suggested, start a new game and name it House Builds. Then you can bulldoze all of the lots and you have plenty to build on. Just be sure when you're saving a house for the first time on a bulldozed lot that you use Save As and save as a new build. I can't remember the exact commands but if you "overwrite" the bulldozed lot, credit will go to the original EA creator for the original lot rather than to yourself.