I don't currently have any investment properties, but will likely work with a turn-key property managment in the Memphis/Little Rock area.My goal is to build a good cash-flow portfolio to ease into retirement. 

This unit has already been indicated by the city that it can be approved as a 3rd unit.

You CAN limit that agreement to a specific property; but, as others have stated, agents are looking for a certain amount of loyalty from their clients.If an agent gets vibes from a prospective client that indicates that they want to cheapskate and not pay a professional for their service, they are not likely to waste their time with them.

Are there specific market indicators or property traits I should be paying attention to?

If the only indication that he is difficult is not wanting to send his ID to a stranger on Facebook, I wouldn't blame him. 

Normally the escrow agent will want mutual sign off even if its clear the contract terms indicate one party should be awarded the escrow funds.

The fact they are complaining online might be an indication the property manager dealt with them properly so be sure to ask the manager for their side of the story.7.

Here is the email received"An internal audit has been completed for STR permits and our records indicate that your STR permit was issued in error due to exceeding the maximum 12.5% blockface density.

In my experience, there are a range of starting-off experiences, but one's experience is not always indicative of someone's desire/drive/commitment to pursue and thrive in real estate. 

Unless the medical condition meets the state criteria for early termination and that the medical notice does not appear to suggest that, you cannot terminate the lease outright/immediately but that you will begin to market the property for rental and upon securing an acceptable tenant, the lease can be terminated pending a satisfactory property walkthrough indicating no damages.