I would say that if you don't need the money, are extremely flexible as to when your principle investment will be returned, do not rely on monthly interest payments and are OK if your principle is never returned at all, than this might be an OK option.

[Relying on an AirBnB success story would make me very nervous though]. 

Don't look at Zestimates and think they can be relied on, as they don't take all the criteria into account.

I'm doing this more as a hobby and have been relying on the small Milpitas library rooms.

A pyramid scheme relies on recruiting other people and paying early investors with money from later investors.

Private money can be cheaper (not always), but these rely on relationships and that takes time to build.  

Also with multifamily properties you rely on numbers and providing value, instead of market swings.I just started researching deals but if you have any questions I would be happy to help!

As far as a great strategy to deal with bad people, relying on the legal system is probably the best way.

That's what they rely on the lender to do...

I’m planning on taking the 90 hour training course so I can sit for the exam and no longer have to rely on realtors for open houses, MLS listings, etc.