For example, I bought a property from a retired soldier that left the area and her management company had been trying to rent for 6 months.

You can transfer your retirement funds to a Rollover as Business Startup (ROBS 401k/PSP) in fund a real-estate operating company.

Half of those folks are in the labor force (others are retired, kids, college students, stay at home parents).

That means is you will get to retire even earlier than you planned!

You would think that we would have at least one success story by now or one "financially free" that retired from buying a course or coaching and following it.Also, the coaches refuse to do deals with students.

But the father and son are both dead now and the wife is semi-retired and I am not interested in buying anything in NJ anyway.

Mostly retired folks in the area..not a high end area but definitely not a warzone. 

This is for long term "early retirement" in 15 years investing.1) location (neighborhood, elementary school)2) price3) appreciation potential- I want the rent to appreciate higher than inflation to preserve4) size- I appeal to families.

Just hoping to get your knee jerk reactions to the idea.tl;dr: If I buy a 3 or 4-plex, let my broke retired parents live in it, and AirBnB the vacant units, would that be a net-positive or a net-negative for me?

The ROBS 401k allows you to use/combine personal funds, retirement funds and other investors funds and even financing from third parties to finance your new or existing real-estate operating company.