@FusRoDovahThere's a couple ways you can do this.
1. Bring your active sim to the neighborhood, click on the lot and select "Move in Household from Library." Simply choose the household you want to move in.
- Sims moved this way will not use any of their funds to purchase the lot.
- If you want townies already in your game to live there, merge them with the household you moved in from the library (in manage households) and delete the library sims.
- Repeat as necessary.
2. Save the lot to the library, move sims into the lot but choose "bulldoze lot" then after the Sims are on the empty lot, place the house back down from the library. Repeat as necessary.
3. Cheat. (This disables achievements).
- Hold down the bumpers and triggers simultaneously to bring up the cheat window.
- Type in Testingcheats on
- Press enter
- Type in freerealestate on
- press enter
- Move sims however you want.
