It's not a matter of belief. It's a matter of what the IRS says about it.
Dwelling unit. A dwelling unit includes a house, apartment, condominium, mobile home, boat, vacation home, or similar property. It also includes all structures or other property belonging to the dwelling unit. A dwelling unit has basic living accommodations, such as sleeping space, a toilet, and cooking facilities. A dwelling unit doesn’t include property (or part of the property) used solely as a hotel, motel, inn, or similar establishment.
Property is used solely as a hotel, motel, inn, or similar establishment if it is regularly available for occupancy by paying customers and isn’t used by an owner as a home during the year. Example. You rent a room in your home that is always available for short-term occupancy by paying customers. You don’t use the room yourself and you allow only paying customers to use the room. This room is used solely as a hotel, motel, inn, or similar establishment and isn’t a dwelling unit.
PUB 527
