It’s a good move to have a contractor walk through before making an offer to estimate costs and timeline. 

I have a little hard time estimating a fair market value given these conditions as I don't know how much to discount the value of the house with these issues presented.

Best estimate is bad tenants are out near year's end.

If I hadn’t been an expert in this market there would have been many variables I would have had to estimate which is a rookie mistake.

I will also give them comps / rehab estimates for the property as well. 

Economic Timing.According to data compiled by Marcus & Millichap[2], the Portland area has experienced three very important trends since 2010:The average price per unit for apartments has nearly doubledThe rate of employment growth rose from 2010 to 2015 but has since declined steadily, projected to be up 1% for 2020 (estimated before COVID-19)Roughly 30,000 apartments have been built since 2010, with another 5,600 units slated for construction in 2020Most RHA members have enjoyed a solid decade of price growth, rent growth and steady occupancy.

After all expenses accounted for, my Quickbooks is showing an estimated Tax bill of $93K.

We estimated the ARV to be $150-160k.

Much of this analysis is based on the size of the land, how much it will cost to do the horizontal development, and then estimate the cost of the vertical build and ultimate value (aka "sale price")

You can use this tool to estimate future property taxes: https://treas-secure.state.mi.us/ptestimator/ptestimator.asp