Researchers found that Airbnb short-term rentals in NYC are less profitable than generally believed, and that increasingly popular lower-income-neighborhood offerings tend to be for single-room rentals vs. whole-house.

Maybe Airbnb performs a useful function in creating reasonably-priced accommodations in "real" neighborhoods?

Are these rentals legal?

NY State law prohibits rental of all of most houses or apartments for periods of less than 30 days. But renting out a room in a house or apartment isn't illegal, provided that the owner or lessee of the place also occupies parts of it, and the paying guest has access to all parts of it. (Some leases may contain restrictions, but violations are the owner's problem.)

But what kind of health and safety code enforcement is there on these units?

For one thing, no enforcement of anything occurs in NYC unless someone complains.

And that's a problem.