We did have to move all the furniture out of the apartment for cleaning - stored it all in the cellar and a couple of large pieces in the corridor for 2 days while the cleaning and landlord inspection was done. The cleaners would not clean if any furniture was there and the landlord required an empty apartment too.

We told the landlord what we were doing, the new tenants were great and got a good deal on lots of furniture and less hassle then buying themselves, and we got some cash for furniture that would have been a big pain to try and move or sell separately, so everyone was a winner. It's usually when you start to try and fleece people - by "making it a condition" and asking for "as new or higher prices" that you have problems.