Look for components you can separate out and write off immediately (appliances being one that I see missed a lot). 

In PA there are 3 components to the yearly taxes, municipal, school and county. 

Now, some will say you're over leveraged but here's the second trick: there are essentially 4 components to negotiating the terms on a note - price, monthly payment, interest, time.

@Alexander BurkardThese two components dont have to happen in any particular order.I do both at the same time.

What I like about the property:- major components are in good condition.

Production for components of many electronic products is done in China. 

I would also be Very concerned that I26 work may be a detriment to the gross AirBnB rental picture the sellers are putting out there.

Seasoned investors are going to look at a retail property or other assets classes and as part of DD look at what is reasonable as a history for a property and how to validate the credibility of rents and others components of a lease.

Personally I would let him stay, but if he's laxing so much that it's a detriment to his health (and/or property, like are the floor boards falling in because of filth), call the police and ask what needs to be done to perform a health and comfort check (welfare check). 

Still, what I do (which let's be frank, is still somewhat trash) mirrors other comments: square footage, age and life of components, and vacancy rate based.