If you attribute a value to your time, even as low as $20/hr, it quickly adds up to make no mathematical sense.  

Mathematically, it has worked out for me because I bought at a good time in a rapidly gentrifying neighborhood.

Additionally, as Michael SeekerThose are some great questions and to be honest I had not considered many of them at all from a mathematical perspective and I appreciate the feedback.

If I apply that $400 a month back into the mortgage payment, mathematically, I would pay off that property in 13 years and 8 months. 

Mathematically, it makes more sense.  

It's more analytical and mathematical that emotional.

Do surveyors remove the slope mathematically to find the 140 ft depth or do the basically run a measuring wheel down the hill for 140ft?

This is not an opinion, this is mathematical fact.Today someone is not motivated and tomorrow for what ever reason they are.The ONLY way to reliably get motivated seller leads is when they find you, and this is the ABSOLUTE ONLY WAY!

As @Julio Gonzalez mentioned above, this is a very complex process and mathematically intense to be done right.

This is the one reason why I utilize this because it's absolutely predictable that it will follow a Financial Mathematical Schedule of Principal and Interest Payments, as well as Balance reduction.Because the Amortized Mortgage is absolutely predictable, and I for one follow the RULE "If you can Predict it, you can Profit from it", I actually look to Maximize this within reason.So while I put down 20% for an Investment Property to maintain a level of skin in the game and reduction of risk by having an attractive interest rate, I generally take about mortgages around $1 Million or above.That is because the Mortgage, being paid by my renters, will follow a very predictable path, one which will make me a millions as each one gets reduced or paid off.In fact, if you receive ZERO cashflow but your Million dollar Mortgage disappears in 30 years, you have effectively made an average of $33,333 PER YEAR for 30 YEARS.And, if you consider that the Mortgage Interest is deductible, especially for a Rental Real Estate Business, you have earned even more than the Million dollar mortgage.For some reason, this kind of thinking is not taught ANYWHERE that I have seen.