The only Sims you can move out have to be YA or older, or you could move out younger ones as long as an adult is with them.
1. Move your Sim(s) to a different house in the same town. (If you try to use the option that came with IP, you can only move the whole family.
2. Go to Edit town as soon as they've settled. Click on that house and choose Evict.
3. Your Sim will appear on a clipboard on the left. Choose to add him to the library.
Go back to your game, or Save and Exit.
To play the Sim in a new game, start the new game, and choose "Move in household." The sim(s) you added to the library should be available.