On a property like this, I would still like to use the BRRRR model and pull my money back out but am unsure on how to value since it's so unique.

If you have an IRA you can withdraw and have 60 days to repay it, this is good for cash deals and quick turnarounds.  

Some storefronts are so unique that they cannot be really compared.

After that time, the bank may let you apply for an extension – like for another 10 year draw period where you could continue to use the HELOC while you repay it.

You are still learning, and a good friend would want to help their friends gain success also.If they are relying on your knowledge too much, why don't you just point them in the direction of the resources you used when you started your journey, and hope you can leverage off of each other's unique knowledge in the future.

My employer would not let me make a roll over until I retire, but the CARES Act let you make a withdrawal that you can repay within 3 years into a qualified plan and it would be qualified as a 60 days rollover.

Or maybe, continue to hope that my continued search for a real career yields something that allows significantly better repayment of those loans.

The US has already passed the point of no return in being able to ever repay the total debt owed. 

I'm wanting to pick an investment strategy that I can really learn to master, and I know people can make money with any strategy and from that perspective it doesn't really matter which one you choose, however, it seems like every market has its own unique characteristics, which could create some advantages/disadvantages for the different strategies. 

Yes it has many great attributes such as economies of scale, but it also has its own unique risks.