Instructions
Move in with another Sim family. Since you have ultimate control of all the Sims in the game, you can merge two Sim families into one household. This will allow you to move into the neighborhood.
Buy an empty lot and build a house. Those who wish to express their creativeness can build from scratch by moving their Sims into an empty lot and using the "Construction Mode" to build the house of their dreams.
Move another Sim family out of their house. As ultimate controller, you can easily force Sims to move out of their houses, even if they do not have another house lined up, which will allow you to purchase the house. To do this, play as the Sim family and click the "Move" option from the newspaper or computer.