From a tax perspective, you'll want to take what you paid for the property plus calculate the improvements you made to the property during your time of ownership.

The 60% LTV is based on the ARV, and that is why practicing calculating the ARV is an important skill that can be learned over time and with a lot of practice. 

Start by educating yourself with foundational books like The Millionaire Real Estate Investor and practicing deal analysis using tools like BiggerPockets calculators.

A true levelized cost of energy (what the true price would be if it were an actual free market) gets very complicated quickly and it's basically impossible to calculate accurately due to the energy industry being so heavily manipulated by incentives from the government for so long, across all forms of energy. 

I have come to the realization that my calculations are not as solid at I once thought.

It is my understanding that the new owner will have the house at the cost basis of my purchase price, for calculating capital gains taxes or depreciation.For gift tax purposes for you - FMV.For capital gain tax purposes for the recipient - your original basis/purchase price 

The numbers calculated assume 0% vacancy (but I reserve 5% for it) .

Go to an RE meetup and have a couple of the RE investors calculate their monthly appreciation, I suspect virtually all will have done better.  

Calculate tax due up sale and weigh that amongst your options. 

.:1)  I've spent some time lurking here on BP and using the calculators to analyze potential options.