In Europe I've seen both. I rented a place in Finland that was a college student's apartment; he'd rent it on some weekends and just stay with his girlfriend th

In Europe I've seen both. I rented a place in Finland that was a college student's apartment; he'd rent it on some weekends and just stay with his girlfriend those weekends. There are definitely people doing it "as a business" as well, and some of the challenge in using it as a customer is trying to figure out which is which (I prefer to rent from the person who lives there). You can usually tell, from how many properties they have listed, how frequently they have reviews, what their booking schedule looks like, whether they themselves ever stay places or only host, etc., but it takes an extra level of manual filtering. For renting of rooms or couches (vs. renting whole apartments), a much larger percentage are people renting out parts of their own living space, so you stay with the resident and usually meet them or even hang out with them, kinda "couchsurfing for money". Though there are some such listings (esp. in NYC) where a shared rental is shared with other AirBnB renters, not with the permanent resident, and I definitely avoid those.