The two biggest factors that have lead me be able to contemplate retirement before 40 (by retirement I mean leaving the 9-5, not golfing all day in Hawaii!)

We are buy and hold investors with the goal of using the cash flow to retire in 15 years. 

My occupation as a physical therapist can be taxing and i'm already planning toward retirement plan with passive income from REI.  

Also, I assume from your photo that you are also fairly young (like myself) and therefore don't have the necessity for a 15yr loan to be fully invested by a "retirement" age.  

My goal is to be able to secure a true retirement.

We are investing for future cash flow, as we hope to use these house in 15 years to retire early.

Either way I feel both can eventually bring me closer to my goal of retiring from my full-time job by 40 (26 now).

The great thing about using a retirement plan is that cost basis generally doesn't matter.

Though money gets discussed from day one, @Debra Leeson is actually spot on; private lending like this is based 100% on relationships.You don't walk up to any private individual waiving a PowerPoint presentation and expect them therefore, to invest their hard-earned personal retirement money in you, solely on that basis.

First I feel that I am still young enough to be less conservative with retirement "money" and if I do lose it all I still have some time to recover.