I'm thinking about going Berlin just before Xmas to see the Christmas markets, and visit Berlin, because I've never been. I'll be with a friend and DD, so it makes sense to get an apartment. I've been looking at Airbnb, there looks to be some great places, but I understand the rules for Airbnb have become a lot tighter in Berlin. Does anyone have advice on how to spot illegal lets? Any other ways to legally rent a flat for 3 nights? Thanks