@John Kelleyreally depends on exact location, current zoning, what type of demand generators in the area, what’s around it etc...lots of questions to determine highest and best use.

It's more of a price per sf, where you find out what similar lots (similar size, topography (i.e. flat), neighborhood and zoning) have traded for and that's how you comp it out.

Any recommendations for books/resources to help the newbie through the process of how to go from start to finish with the development process and each of the steps involved in buying land, going through zoning and planning, how especially to forecast costs and do the due diligence to forecast the potential to then divide the plot into smaller lots and build duplexes to hold and rent?

Your biggest issues will be zoning, permitting, and financing the additional units, @Martin Phillips.

I can just switch it be my primary on paper but I live and work in NYC which is about 3 hours away would that raise a red flag when when doing taxes or in general?

Mainly looking for things to be on the lookout for aside from liens and the normal red flags.Thanks!

They are reported at the Assessors site as 4-plex's and the zoning supervisor has confirmed that they are legal but now non-conforming as the zone district was later changed to duplex zoning  and are thus "grandfathered-in" and can continue in their use as 4 units for as long as desired. 

I'm a bit cautious about Airbnbs in cities -- I'm not familiar with the regulations in Atlanta, but I would recommend really looking into it and pouring through all the past news articles about lobbying/short term rentals/unhappy residents, etc to gauge the possibility that your rental could be banned/zoning issues/increasing taxes, etc.

To me, this seems like a BIG red flag.

There were a lot of red flags that I won't get into.