Quick update- the first thing they asked was “how much could we sell it for?” . Then the ghost cleaned a mug and poured a cold mug of dwarven ale from a mysterious tap. Deal closed. They’re keeping the manor.
Good outcome. I didn't respond, but I was thinking "Really? They'd want to sell a house that has both a bar and a ghost?"
I would think a better question is: "How much does it cost to excavate a dungeon underneath a manor in Waterdeep?"
This is why we couldn't have nice things in 3e and 4e. Because while a bar and a ghost would be cool, the 10,000 gp you'd get for a manor home/ tavern would get everyone +1 weapons.