And with that, the investors have to hold themselves accountable for whom they selected, ever wisely or foolishly, to invest there $ behind. 

I was mainly thinking about the effects of putting an entire strong cashflow back into the mortgage.

How do I design a small yet effective real estate portfolio?

It binds the landlord, but honestly has little binding effect on a tenant when they simply choose to leave.

There is also algorithm advantageous to bi-weekly vs monthly, so a bit of a credit-hack boost effect to it. 

The section 8 policy on treatment of tenants had an obvious effect as the hit to dignity caused them to move. 

Tons of jobs and growth which allow for better tenant selection, low crime/safe, etc.

The irony of the 1% "rule" is that those who could even use it effectively don't need it, ie if you need to spend more than 30 seconds thinking about whether it fits the guidelines you're probably not educated enough in RE to use it anyway. 

It's a type of house hacking that's very effective to get your foot into the real estate investing door. 

So 1031 effectively reset the qualified/non-quaified use of prior owned property.