I am trying to virtually have all expenses covered housing with the house hack and perhaps air bnb.

If it's not from the ductwork it is likely a roof leak, but being that it is concentrated around the return that would be what I would look at first. 

Most lenders require you to show you have the money to cover down payment, closing costs, and at least 3 months in interest reserves, but not all lenders require it.

I literally could go buy a few houses cash that'd likely cover my entire rent let alone the small portion I'm actually responsible for.

Thank you, Jason, so for a BRRR you don't use COC, you just look for a property that will be able to get a loan that will cover your original invested cash? 

In the process of doing this BRRRR I had to deal with a broken water supply line at 6 am, a roofing contractor that didn't do a good job and left my roof leaking in various spots, and a call from my new tenants saying that the house was flooding because apparently, as we found out later, the plumber didn't weld the copper supply lines to the shower valve correctly and water was coming out from the wall.

Or if your primary has any equity go open a HELCO to cover the money needed and once the refi is done paying it back?

This is covered extensively on Bigger Pockets.

Being in Houston could make it difficult to find more than 2 units under 1 roof. 

Hopefully, the home debt will be covered by your rent collected and you will not have to pay any of that out of your pocket.