There's a house for sale in South Carolina that is a duplex. But it's listed as a single family dwelling because there's a permanent tenant upstairs. There's a message to the people who buy the house that they should never go into the upstairs apartment, they won't get rent or a deposit, and they should never ask questions. That's way too creepy for me but maybe someone will find it intriguing enough to buy the house. It's listed on Zillow and some have called it the "nightmare house."