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.

If you're looking for rent estimates for MTR, there is a great tool called Pricelabs.

There are also many calculators out there that over estimate the cost assumptions or rent comps.

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

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

The new released estimated total of the effected areas is now in excess of $250 Billion.

Land is very tough to estimate value do to it's valie is based on what you can do with it and how much demand there is for what ever is ultimately done with it. 

Question is, if I have the means to put a high enough down payment on a house to be cash flow positive (assuming my expense estimates are accurate, etc.) is that something that I should do?  

Quote from @Hector Espinosa: Hi,I'm negotiating a seller financing deal which may be my first one and would like to ask for some advise about and what are advantages and disadvantages about seller financing deals.These are the seller financing terms:House Price: $330,000.00 USD​ (Sellers still owe ~$301,000 USD)Down Payment: 5% = $16,500 USD​Loan Amount: $313, 500​ (Monthly payments will be amortized as a 30 years loan​)Interest Rate: 4.531%Balloon Loan Term: 5 YearsMonthly Payment (P&I): $1,594.24​Closing Costs:  ~$3300 ​Zip Code: 74105Observations:       * HVAC requires an update but pending to inspection (replacing with a new one will cost ~$10,000 - $15,000 USD )     * Expected Rent Income: $2,000- $2,300 but this is has been really complicated to get a good estimate because is all over the place in the different sites I have checked

What do you estimate is the difference between the market rent (or what other tenants pay) and what she pays?