Can you help with a title of a horror movie?

The movie begins with a woman (possibly a real estate agent) who enters and abandoned house and gets killed by an evil entity. Later that same day a college fraternity throws a party at that same house and people start dying. The female protagonist later gets possesed by the entity. I remember someone falling of the roof of the house but doesn't die. I can't remember how the movie ends. It came out in the late 80's or early 90's and I don't think it played at the theatres. Does anyone know this movie?