I really liked the multi unit concept even though I had never seen anything like it before (or since) and it made sense on paper although it looked like a bad deal from the visuals.

I should add to my answer above because I failed to address one of the most important concepts:  Incentive.There is an insinuation here that recapitalizing at a below-market basis is inherently advantageous to the sponsor, and thus the sponsor has some incentive to “shortchange” the original investors.So how does one insure that this doesn’t happen?  

I would also like to know what do people think of this fairly new concept of "Rental Arbitrage".

Another thing to keep in mind is that some HML's aren't super keen on the idea of financing a first time flipper- HMLs that will lend to first time flippers do exist obviously, just don't be surprised when this question comes up from one.So here’s an example deal; (Just trying to make sure you have an example deal to see how working with an HML would work and in my quick typing I may have gotten something wrong so please use just as a basic outline for an idea in concept!)

If you are going with a bar concept you also need a license and it's expensive- if there is a school, church, or conflicting use nearby it's going to be difficult to get permits and license.

The ROBS concept is different, in that your 401K can invest in your business without taxes or penalties, but the business itself remains a taxable enterprise. 

I am not fully understanding this concept.

I am not fully understanding this concept.

Similar concepts have been tried by others and failed. 

Interesting concept no matter especially if one is sitting on a mountain of crypto.