If you follow the trend, Wicker Park turned around and the gentrification continued Northwest up Milwaukee all the way to Logan Square and now Avondale.

@Alex Chin Hilltop is HOT right now (has been for a while but the trend will persist).

If your margins are too tight you can go from cash flowing to breaking even given this trend.  

That trend is likely to continue.

Look at the neighborhood trends, whose moving in and who is moving out. 

There is definitely a gentrification trend happening, at least in the Charlotte area.

I'd stick to a particular area, so that you will understand the trends and know when a good deal is available.

I'm actually working on putting together a web-map/application to help me analyze property metrics and market trends.

Im moving closer in the direction of my first purchase for a multiplex...I have a decent amount of money able to be used as a down payment and have a reserve, I started an LLC last year, I continue to learn about real estate investing and study market trends in the area, I put together scenarios and run numbers using real homes that are listed on the MLS, but I continue "what if-ing" everything to death and then back out. 

If your first in on the neighborhood that can also be scary and unless you have deep enough pockets to start snapping up multiple houses to cause an upwards trend I would allow someone else to take the risk first.