Move In and Move Out should not empty the house/apartment. I checked in my game and if a household move the furniture are still there. Only dead remove all furniture and I think this is to blame for you empty houses/apartments. Which is of course stupid if you have aging on and all sims dies in their home lot.
You could use the gallery and just replace the home with a new one? If you use the hashtag: *playtested* you get houses which are normally functional. (If you are console player avoids houses which are build with T.O.O.L the cause problems (low fps, lag and all other funny things)
