The Secret Sex Lives of Ghosts by Dustin Reade

Thomas Johansson can see ghosts after a near death experience, and has made a living killing them for a second time. After discovering that being possessed by a ghost causes an intense hallucinogenic effect, he goes into business with a perverted dead man named Jerry, selling possession as a street drug (street name: Ghost). But is the farmhouse he sees while possessed really a hallucination? Or is it something else?