I don't deal with the air b and b things much but I believe that status has tax implications too. 

Renting out bedrooms as an air bnb might be over-whelming based on what others have said here.

These sites have very generic and do not take into consideration things like, building codes, zoning requirements, light and air requirements, site orientation, utilities, soil capacity for foundation types, etc.

central valley up to Lake co.. look between Redding and Woodland etc etc there are plenty of places you can buy that will cash flow.. without going all the way across the country.. you could look at student rentals.. you could do air bnb in a place like Portola  Greagle  plenty of places to buy in CA.

The problem is steam pushes out the air through the radiator vents and vents on the mains.

Have I been watching the Idaho Painter too much on You Tube?

That's also why I put air quotes around "hidden" because if you actually look at the leases this can be missed.

Best of luck in your market.I'm sure you'll get some stories...lots of "hot air" around here ;) Just remember that investing is relative to your individual goals, needs, skills, abilities, and resources...just because it worked for someone else doesn't mean it's a good idea.

We hired an "environmental hygenist" to test the mold and air to determine what the mold was and how significant. 

I have had them create listings out of thin air - listings that simply never existed, and I have seen WILDLY inaccurate Zestimates.