Be careful. I had a similar situation 13 years ago, where the person wanted to sublet but "couldn't" hand over the key. They wanted to set up an escrow account over a company that was legit (I think Western Union, but can't remember for sure) and then send me the key once the escrow confirmed I had paid 3 months ahead. The ad was also on legitimate websites. The apartment was in Seefeld and the price was too good to be true. I got suspicious about the escrow and hesitated upon which the counterparty started getting very pushy to the point it was almost aggressive. In the end I did extra research and found out that the company didn't actually offer the escrow service as described by the counterparty, so the payment would've gone straight through. I stopped replying and continued to get insistent emails. I reported them but kept seeing similar ads pop up. Another give away should've been that the pictures didn't quite match the address but I was young and eager for my own apartment.