> In a case like this, renting out the entire place when the terms of the rental is that the owner won't be there, this exception wouldn't seem to apply, though Idaho may have different rules (I'm having more trouble quickly finding a good description of Idaho's rules.)

Good luck, there's not much for rental regulations in the state of Idaho, and literally nothing for short-term rentals. It would come down to whether renting a property on AirBnB constitutes a lessor/lessee relationship, in which case the Fair Housing Act automatically kicks in.