More than one chef in the kitchen, something will eventually fail. 

Your story captures the essence of what Napoleon Hill talks about in Think and Grow Rich.

However, in a more commerical context, lenders may want to capture that anticipated profit from the prospective interest payments, so they will add in prepayment penalties.

Oh and while I'm blabbing, the idea of capturing $100-200 / door as cash flow that I have been seeing in other discussions or hearing on the podcasts are these folks considering the COC on this?

If you buy a previously $100K home for $50K and rent it out, and over the coming months and years it "recovers" to $75K, you have captured 50% appreciation.Since rents have not dropped anywhere close to 50%, you are are more likely to cashflow in the mean time.

So for primary, I'll capture 500k tax-free ; and  1031 for other rental almost simultaneously; with the new acquired property is a duplex as mentioned above ?

Both parties seem to have been captured by their extreme nutty wings.

It allows you to purchase investment property with a minimal amount of money out of pocket, while allowing you to also capture a lower interest rate.

That has allowed us to accumulate data on serial tire-kickers, which saves us time in dealing with them but it also allows us to capture pieces of data when they interact with us or our web inquiry forms. 

A much higher equity capture.