I had no idea about the obstacles that needed to be overcome in getting financing, finding deals, etc, but I kept learning and reading and at the same time finding a job where I could have steady income while I continued to learn.

That puts them in a tough position because they often don't have the resources to continue on their own. 

There is a married couple, with 2 kids that claim they have (570 credit score), that their credit issues are over 5 years old, both are holding jobs for over 3 years, with enough income to cover rent, and they are willing to provide a co-signer.Should I just continue to wait for the application that qualifies completely or should I look into this one more? 

Doing that and continuing to pay down the loan should allow you to reset the equity at some point through refi or heloc and roll that into a new property.

From what I am reading/learning, I believe my goals best align with a buy-and-hold strategy for continuing cash flow (BRRRR?).

Barring something catastrophic, our prices will continue upward. 

I would continue to make your payments and leverage your lump of cash to purchase an asset. 

Ola Dantis There’s been a lot of development in The Washington and Benton counties of Northwest Arkansas going on and there still continues to be.

I have read varying articles saying between 1.5 and 7%3) How do we determine the monthly rent and rent credit?  

Likely 1-2 years as  long as you are frugal and continue to sustain a solid savings rate.