You could also get hit with a huge lawsuit if the units are not up to code and a tenant gets injured, or if a vindictive tenant turns you in.Get the seller to get a zoning exemption and make the duplex legal, or get a substantial price concession, so that the deal makes sense as a single family. 

@Eve Oliver Dorian Gray from Sherwin Williams is also popular.

That being said, the area is still very popular.  

Contrary to popular belief, you can evict even if they are paying on time, if the property is getting damaged.

But 30318 and 30314 are coming up (30318 is a huge zip code so obviously some it has been popular for years) but the collier heights area and anything along mlk has gotten better as well as the north part of 30318 below riverside and west of Howell station area.

I know you want to narrow down your list to meet certain crieteria, but how do you actually find that criteria and the names of people who live in a neighborhood that is popular with cash buyers?

Two of the most popular areas for multis got flooded really bad in Irma so be very careful and make sure you do your due diligence.

My point is that the set of things I've seen here are pretty familiar to the various popular hobby/team/career forums. 

The sub forums for the states are not as popular as the more generalized forums.

Some of the other popular cash flow markets have very stagnant jobs and populations.