If I wanted fresh air in the apartment, I would, however, leave them cracked a few inches at the top and bottom, but I would never leave them all the way open while I am gone for hours at a time.For reference, this apartment is a 2nd floor apartment and on these particular windows there is little overhanging structure to help keep the rain out.

I left it with existing windows, 40 year old oil tank furnace and no central air because I was already at the limit of what that house was worth (145 was the highest price for that model in recent history with average of 120-130 for less rehabbed ones).

I had all kinds of things break my first year of ownership.People often overlook things like water heaters, water softeners, furnace, and air conditioning. 

I’ve had so many plumbing leaks like this over the years, I’ve found it saves a ton of money to just deal with it myself: fix leak, pull everything out, use an air handler, big old dehumidifier, fans to dry it all out, wipe off the mold, spray some bleach, replace drywall, put it all back together and I can usually get it done relatively quickly for a couple grand and move on without having to mess with getting completely gouged by sketchy restoration companies or insurance (who just raise your rates or drop you).

Awesome way to make money from thin air  

Hey BP family, I am closing on a duplex at the end of December and one of the units is currently an air bnb.

Let me know what area of town you reside on as I’m about to start building another SFR and another builder buddy got one up in the air.

I would think about 10k to 12k should be a reasonable price to do all the duct work, condenser, air handler.

Another thing I’m wondering who I can contact to see local air bnb laws and rent by the room laws.

Have you considered renting by the room or air B&B'ing the property?