My instinct says that the county record data is likely the most accurate, but was curious too if anyone knew what the Driving for Dollars app uses for its skip tracing because I've been getting different results with my own skip tracing.Appreciate any insights - thanks in advance!

Does anyone have any advice on how to troubleshoot this issue with future clients and how accurate can these services be if I run into this problem at least much more than I anticipated?  

While doing that, I faced some hurdles around getting accurate economic, demographic, and real estate market data that didn't require a big software subscription and was also hyper local.

Here's the general info I have gathered from MLS, and local tax information.

Eventually you will need to be able to do this accurately on your own. 

Its best to gather at least quotes from 3 reputable junk removal contractors in your area.

As @Wayne Brooks stated above, It's well worth a hundred bucks or so to pay for a title search to get a complete & accurate picture - especially before you drop $30k on an auction bid!

For newly constructed, purchased or renovated properties and also retroactive generally over the last 10 years, building components are properly classified into individual units of property and accurate recovery periods for computing depreciation deductions.

I believe most of what you wrote is fairly accurate.

Property Taxes ($3,442):  accurate.