Lets start with when it does not make sense: Owner finance does not make sense when the borrower cannot afford the property. 

I choose that market due to affordability, potential cashflow and cash on cash return. 

I'm currently biased towards Indianapolis based on its job growth and affordability, but you could honestly find deals in any of the markets you mentioned (and if your heart is set on the Atlanta metro area, I'd strongly suggest the towns Union City and Fairburn based on their growth, appreciation, and price -- I almost closed on a good BRRRR deal in Fairburn but the rehab was just out of my budget). 

Even including modest appreciation and equity pay down, the ROI is between 7% and 12% for a non passive holding (not good for an active holding)I can easily afford this level of negative, but do I want to?

As lenders, well issue a prequal/preapproval letter if we've analyzed your income, assets (bank and brokerage statements to establish that you have the liquidity to afford the down payment, closing costs, and reserves), review credit of the guarantors, review the relevant experience to ensure that we're not throwing our money away on newbies that are wandering around in the dark, and have put together a reasonable plan of attack for the project.

It offers affordable housing, solid rental demand, and generally favorable landlord laws.

What exactly would make a city board approve non-affordable (i.e. not Section 8)  apartments?

I can certainly get you quotes but based on my experience the market is becoming relatively affordable. 

If you can afford it I would look north towards Tompkins and Schuyler counties instead.

They have degrees and interests in different segments of what I think are important facets of the real estate game, one will be graduating with a degree in construction management and the other in accounting.