Moans from the walls

Professor P gave us the strangest hypo today:
Professor P: “Jack. Lets assume that I want to sell a house, and you are my broker. And lets also assume, for the purposes of this hypo, that the house I’m selling is haunted.”
Jack: “Uh…well, since that’s not possible…”
Professor P: “Let’s assume that it is possible.”
Jack: “Okay. Well, it’s not necessarily physical defect. Ghosts aren’t damage to the property…”
Professor P: “But the moans are coming from the walls!”
Then it was Jill’s turn.
Professor P: “Now Jill, you are a consumer protection advocate. What do you say?”
Jill: “Haunting is a material fact!”
Professor P: “Is it?”
Jill: “Uh, I suppose so.”
Professor P: “Let’s suppose that the walls don’t moan that often, or that they only moan at midnight.”