I had several clients over this past summer who had issues with selling parts of their houses. Specifically, the offer didn’t mention something that the buyer had every right to assume was owned and would be transferred (whether a hot water heater, water softener or furnace), the buyer had not agreed to assume a rental contract, and the item was actually rented. In each case, the seller had to come up with the money to buy out the remainder of the contract to be able to give it to the buyer.
If you have rental items in your house, it is critical to ensure that they end up in the offer properly. You can have the buyer agree to assume the rental, but only if you tell them that it is a rental. If you’re not sure, check before you list your house. It can be a very expensive omission.