If you have grounds for a reduction, recent arms length purchase or neighborhood comparable sales that prove a discrepancy in value it’s an arduous, but not difficult process.

Looking for information on how to find Investor-Renovator interested in purchasing residential condo in As-Is condition.

@Shawn Evans, your family member selling and doing the 1031 has to be able to take title to at least as much real estate as they sell and use all of the cash from the sale in the purchase. 

The assumption package provided by the current mortgage holder is fairly straight forward except that it states we need a "sales (assumption) contract between seller and buyer."  

This will allow you to provide more accurate home sale comps in order to determine the ARV.

@Robert LindsleyTypically, either comparable sales in the area or using the cap rate.NOI/Cap Rate = Price.

Ask around about who is the best tax sale resource in the group...or outside the group. 

I'd go to zillow.com or one of the other biggies and look for comps in the same neighborhood, especially the "recent sales."

It's likely I will not have to pay them for anything related to a purchase or sale (included with plan), therefore I'd like to have someone experienced. 

Between the outside condition and the fact that it is up for a tax sale, I assume the interior is trashed.