Instructions
Find a Sim who would like you to build her a house. Open the "Relationship Book," and scroll to that person's name to see her interests. Build a house themed around her first interest, such as studying or spooky things.
Walk around your town to find an empty lot where you may build a house. Walk onto the lot, and press "A" to select a block. Place the block where you want it, and press "A" again to release it. Use the "Up" and "Down" buttons to re-size the block, if necessary. Use the blocks to build the frame of your house.
Add a roof, windows and doors to the house. You may also add decorations at this time. Check the Sim's "Interests" page and only add items that match her primary interest.
Paint the building, the doors and the roof. Click on "Done" to move the Sim in.
Build two more of the same houses next door. At random, the Sims who live in this neighborhood may throw a party on the lawn. You can join any party with fewer than three Sims.