if you mean, buying walls and setting them up, putting in carpet and furniture, you can't. you have to get into the game to the point where Dr.f gives you another create-o-tron or whatever he calls...
I hear that you can't,you can only buy pre-made ones,and that is the egxact reason I'm not going to get it now,because half the fun is building houses from scratch.
To get a new house on My Sims Kingdom For (DS) go to Toronto and he builds houses. Simply bring him the blueprint, the essences, & Build it! Then go to one of your 3 houses and switch it out with...
You just have to build wall around a lot that you buy and you add rooms and then floors and wallpaper and then furniture and stuff. It is really hard to tell just experiment and try.
Answer
You...