If it doesn't have a means of its own propulsion, used for such or not, at least there has to be a motor hanging on the stern AND it has to have holding tank for waste. I stayed on a lovely 1000 sq ft home in Lake Union one night that looked exactly like a houseboat, upstairs was helm station never used, two Hondas on the stern, large holding tank pumped by person who comes around weekly on the lake. Houseboat? Boat like a house? Both really in this case.