I've seen this before where the building is only on AirBnB because it's zoned residental. I once stayed at an AirBnB where the little welcome binder you got when you got to the room included instructions on what to do if the cops knock on the door and start asking questions.
It's one of the caveats of bargain hunting. Sometimes you end up in sketchy situations.
Oh, I stayed in one in Xiamen like that. AirBnB did not make it clear on their website that in Xiamen AirBnB's are illegal (some cities in China they are legal and have a deal to do hotel registration with the police for you). We arrived to a pile of notices on the door "This is an illegal hotel, etc etc". Not super fun.
It's one of the caveats of bargain hunting. Sometimes you end up in sketchy situations.