The Executor by Jesse Kellerman
Things aren't going well for Joseph Geist. He's broke. His graduate school advisor won't talk to him. And his girlfriend has kicked him out of her apartment, leaving him homeless and alone. It's a tough spot for a philosopher to be in, and he's ready to give up all hope of happiness when an ad in the local paper catches his eye.
'Conversationalist wanted', it reads.
Which sounds perfect to Joseph. After all, he's never done anything in his life except talk. And the woman behind the ad turns out to be the perfect employer: brilliant, generous, and willing to pay him for making conversation. Before long, Joseph has moved in with her, and has begun to feel very comfortable in her big, beautiful house.
So comfortable, in fact, that he would do anything to stay there-forever.