Now that I'm more educated on this stuff I want to invest that equity into a better rental.I can have the tenants go month to month at the end of their lease and then non renew.

So it's an outlier I want to be educated on before I sell. 

I wonder, as Atlanta continues to grow and become more dense, if the code could be reworked to allow for more properties with basement apartments?

Further to decide if you should continue to own it? 

.- Continue accumulating SFR rentals.

Separate your desire to invest from your education/career goals.Always keep in mind when it comes to education if you don't enjoy what you are doing you will not do well.

He got married, moved out, costs have gone up, and he made a few adjustments, rented out the 4th bedroom and continues to hold it.

Where can I educate myself about the intricacies of buying from the Sheriff sale?

It's in a great area that will continue to go up in the long term even if it dips in the short. 

I would recommend looking into West Kensington, Frankford, and Port Richmond-  You can still find great deals there withe excellent cashflow, and I believe the path of progress will continue to march into those areas and increase values.