With the massive increase in STR properties in the US, I am hopeful that lenders and appraisers will evolve to apply income/exp metrics to STR deals specifically, on top of generic property comps.

As a builder/investor myself some of your estimates seemed a little off to me, but those can be very market specific so its hard to say. 

Most of the other posts provided general information that is good to know but did not answer the specific question. 

This specific deal was a close friend's apartment that he was renting.

I was wondering if your willing to share some more details specifically regarding expenses, maybe hop on a call one day with me? 

It couldn't hurt to call a couple attorneys right away to see what they say in terms of cost and suggestions for dealing with this quickly.In terms of mitigating any legal issues with your tenant be sure you are documenting every conversation you have had with the HOA in terms of asking them to make the necessary repairs.

DSCR loans are a great option for investors looking to scale their portfolio as they are property specific and allow you to close in an LLC

In most states, Airbnb rules are city and county specific.

Purchasing the LLC gives you ownership of the property, but it also opens you up to additional legal exposure since the entity has been active, and there is no way to really know for sure what else they used the LLC for.

Is there any legal action one can take or is it just a lost cause?