6.125% has P&I of $2625/month.5.75% has a P&I of $2521/monthThis is a $104 benefit.Paying $4400 more towards principle will reduce your payment to $2598, a $27/month savings.Math says buying the rate down has a larger net benefit to you up front, but it will take you 42 months to break even.

Rentals boil down to how much do you net after paying principle, interest, taxes, insurance, and a maintenance reserve.  

I plan to pull my principle investment sometime soon and keep a balance of it. 

The principles would still be valid though 

@Michael Camacci, KP is Key Principle.  

Like aircraft checklists and vehicle operators manuals (the -10s), one can benefit from extensive research, trial and error, and deliberate improvement principles gained by the many that have gone the path before. 

Alignment of interest between management and investment capital is a cornerstone principle that is never compromised.

I'm eager to meet and collaborate with fellow investors and industry experts who share my goals and principles.

The principles in the Academy are aligned but what sets it apart is that with Nate it's a more granular level.

If you have mastered RE principles, assessing the value of the collateral is fairly easy.