.-- When you find a good cleaner, pay them well to keep them.

That said, South Collier Heights, especially near I-20, seems a bit further along—"better" in the sense of being safer from what I'm seeing.Bottom line: real estate in Atlanta is extremely localized right now.

However there are cases where we pay for some.

I’m never a fan of paying taxes today that you could avoid in the future.

With the current 80% bonus depreciation, it translates into a $40k deduction and $10k in tax savings, give or take.

I will sell this property in order to pay off debt.

Paying off a loan with the funds may not qualify.

Is it better to put a larger down payment to reduce monthly mortgage cost or to pay principal to reduce the length of the mortgage and time spent paying interest?

What you are looking for, based on your list, isn't out of line. 

It's already a known challenge with sunk costs.So, pay close attention to your monthly statements and, assuming you have a PMC, chat with them at least monthly for 30-45 minutes to learn more about how they are managing your property.BTW - w/o you doing more research than you did before buying these two properties, STR will just be the next "shiny object" you gamble your money on!