So the rules of Monopoly state that you can't buy a house if there are no houses left for sale. You can't even pay all at once and buy a Hotel if there aren't enough houses to place 4 on the property first. But, what happens if you have a hotel in a property, all the houses are gone, and you want to (or are forced to) sell your hotel? I'm guessing that you are forced to go ahead and sell the hotel and all 4 houses at once?
Yes, you can only downgrade a hotel to a number of houses if that number of houses is actually available in the bank. If there are no houses, you must sell the entire hotel outright. This fact can be used strategically: