Possession is Nine-Tenths of the Law — Ian Rogers

Jerry Baldwin sells haunted houses for a living.

A dangerous job--but in a world where paranormal has become the norm, someone has to do it. When the daughter of a former client ends up possessed by a supernatural entity, Jerry enlists his friend, private investigator Felix Renn, to help him perform an exorcism. Unfortunately, Jerry is a better salesman than he is an exorcist, and he soon finds himself in over his head, despite the best laid plans of monsters and men.