I will stay at the airbnb at least once (probably more) to come behind and check that everything was properly taken care of, but I can't make that trip constantly.

if you are near the end of the lease for the tenant you can list it with seller notes saying currently occupied and will be delivered vacant by end of escrow and make sure to give the proper notice to the tenant that you will not be renewing it

I found a off-market deal about 2 months ago, and I was about to close the deal, but apparently the owner has some tax problems.They owe 6k at the county and from what he said " there was an issue where their payments were not being properly applied to their account for several months and they can't even make anymore payments until the company tracks down the payments they already made".

I have 209,000 purchase agreement executed and the comps show the house should go for 299000. 

A proper lender will be happy to oblige.

This way you can properly screen them and establish a clean /proper lease.

Simple solution: execute the contract as agreed to.

Yes, if you took possession properly and did not use self-help.I may have missed something here.

I have one but am unsure how to properly fill out.

I wrote an entire article on how to properly structure your cash/HELOC purchases HERE.