Yep it's really easy, I'll explain how. When you make a fresh Sim they are put into a household bin, well all you have to do to put a Sim and a house is click ''Save Copy to Library''. You can also put a Sim this way, with all money included. If you want a one Sim in the Library, like I do sometimes, just evict the others. Clicking the evict button won't work because all of the Sims will be evicted, you have to use ''Split Up Household'' button to get one Sim. If you want all the Sims and house just click ''Save Copy to Household''. It'll save everything the house has and all the Sims. I wish I had known this when I first started playing, I'd still have my first Sims. The menu pops up when you click the map tag for the house, the active household has a little house icon, but the map tag is green, instead of blue. I hope this helps you out and I didn't confuse you.
Edit: When the house is in the household bin or Library as I call it, you can move them to any town you'd like. I have a Sim I keep a copy of and use alot. The best part is they never get deleted unless you delete them.
