I have five houses in Memphis area, and the biggest problem has been finding a good property management company. 

Their pro formas felt optimistic with providing 6% annual appreciation and property management that is only about 6% of rent so I take it with a grain of salt (they offer their own property management services but it has terrible reviews on Yelp so I would probably go with someone else). 

For example one person could manage paperwork and another person could be boots on the ground.

@Steven Wetherillwhat about property management?

I personally like to buy in towns/neighborhoods in which no new builds are possible within 10 miles because all the land is developed.

Your experience reminds me to manage the portfolio well (i.e. sell losers) and to be patient. 

Flip to another developer looking for your zoning ordinances.

I also have a ton of property management experience and offer tenant placement.

I've managed up to 400 rentals and never offered a concession.

The other 10% are scammers, or have mental issues, or have perpetual money problems, or are career criminals, or psychopaths, or have massive entitlement issues, lack anger management, or are spousal abusers, or can’t hold a job, or don’t want to work, etc.