Blue tarp on the roof, lots of trash in the front yard, and it's very apparent that the house has not been washed or painted in years. 

So unless you speak directly to the previous landlord, you wouldn't know.If I'm wrong, I don't believe I'm far off from the truth in this matter.Also, how long was he on this "steady good paying job"?  

As soon as waste starts washing into your field lines, your days are numbered.

I think it pretty much comes out as a wash for the most part as far as taxes go.  

Down payment and the entire home was renovated- a full bath was added, central HVAC and heat pump installed, upgraded hot water heater, entire back 1/3 home: new insulation, drywall, and trim, addition of laundry room, fully furnished and new appliances.

It wasn't totally worthless, but if I didn't already have my long term rental business that I could piggyback this off of I think it would have been about a wash in terms of value (ie the bookings I got I probably would have got anyway on Airbnb or VRBO). 

Why was he so far behind in rent?

Are you cleaning every room and doing all the laundry?

Wash your car perhaps?

Wash, rinse, repeat, and pretty soon you won't have much of a list of contractors who will even pick up the phone when you call.