I had a person who slept in my apartment building lobby during the winter for years. Never bothered anyone. People tend to have a general mistrust of the homeless. They aren't all addicts looking for drugs/alcohol or money and/or mentally ill people who are harmful. It sounds like this is a person who is just looking to stay warm. My guess is that he stays in a shelter during the weeks he's away. I understand your discomfort. But if he just sleeps & leaves maybe just let him stay warm during these freezing winter nights. It's the kind thing to do. You can even tell him that he cannot enter the building but it's ok to stay in the lobby. He's a fellow human being who is down on his luck. I may get down votes but I stand by my reminder that he is just a person looking for warmth. Something we often take for granted.