But we have remained debt free & retired for decades & have never had a mortgage on any of our homes or any of the investment properties we own, (but we still hold seller financed notes on the majority we have sold). 

If you give notice and they remain in the home beyond the termination date, then the next step would be to evict.

Without that, you could estimate what the remaining time would be based on the original starting amount (public record) and then just do a 30 year amortization with the approximate interest rate at that time

Thus, my own bias of course, I think the best use remains residential.Is it possible to challenge or request a second opinion on the appraisals "best use"?  

It is very important to understand what you are purchasing at the sale and whether there may be any liens remaining on the property.

The attraction to business investing however has remained low due largely to the unknowns.

I have since sold one lot for more money, and the remaining lots to a second buyer so with closing costs and such I will still be at the same profit margin.

Until the ENTIRE screening process is complete (the means the applicant has provided ALL the required information and has met your screening criteria), the lease is signed AND the security deposit and first months rent (plus pet fee if indicated) is provided, the rental unit remains on the market.Early on I had an applicant (a 100 percent service connected veteran) sign a lease but ask me to hold off on paying the security deposit and first month rent until the first of the month when he moved into the area. 

I just assumed that the property tax would remain at the property value, not sale price. 

The remaining profit is an distribution, which is not subject to SE tax.