Often times properties are priced right, so your equation goes out the window.

What you're actually doing is erasing the profit from the equation.

I thing that pretty much answers my question.I looked at an amortization calculator and compared the differences and it would equate to them spending about the same amount each month.Unless...

Would I just build the expense of the loan into my "do it or not" equation?

That being the case, your ~$50K equates to ~$3K in monthly take home pay.

The onsite management is pressured by their bosses to have low vacancy numbers even though it has equated to less revenue.

You can find when the subdivision was platted and when each lot was sold and each home was sold through title work, but I usually just drive trough and I can tell about when a home was built and how the neighborhood was established, but it doesn't equate to any profit on a single property.You may be looking forinteresting but useless data, maybe that is why it's hard to find......

So instead of the mortgage payments being on the top of the equation, they will put the income from the property in the income (bottom) of the equation and it helps you qualify to borrow more money.  

What you did catch me off guard with was your FMRR equation.

If your buyer "might be" this and "might be" that, then take the "might" out of equation.