Housemate Emma sitch makes me nervous

The letter writer who's moving into an apartment situation where Emma's boyfriend's apartment is in the same building needs to be prepared to establish boundaries about the boyfriend entering their apartment. He should not have free access where he thinks he can walk in uninvited. He should not be given a key. There should be boundaries about him staying in the apartment. Given the proximity, it will be very easy for things to slide toward him being around a lot.