Since you are just getting started, I'd concentrate on working with sellers first and getting your own buyers list in place in place of agreements with other wholesalers.

But as I stated, I want to aggressively pay down the loan so not looking to cash out ReFi or DSCR and just concentrate on clearing it. 

If that's the case, then your next best bet is really concentrate on your studies.

Before I talk about how to select a tenant segment with a high concentration of reliable people, you need to understand the relationship between a tenant segment and the property.Every tenant segment has specific housing requirements.

Therefore, you should buy properties that attract the segment with the highest concentration of reliable people.Each property attracts only a single tenant segment because its characteristics match only one segment's housing requirements.

Now that I’m in my early 70s, I think that’s TOO MUCH concentration.  

You're correct that the Clark/Fulton area is a bit rougher and is known for having a higher concentration of Section 8 housing.

It's amount of WORK and CONCENTRATION that will make a difference between make or break, and no GURU can make you stick to your regimen and do something persistently and systematically if you can't make yourself do it.  

We've negotiated some in a portfolio where a certain house will be at 25-30%, maybe even as high as a 35% but the loan is less concentrated in houses with less of a downpayment(10% needed for a STR). 

Therefore, identify a tenant segment with a high concentration of reliable people through property manager interviews.