Following this one. 

I just type in on Google "rent vacancy rate in BLANK city". For the city that I was looking at, I also was able to find rent rates for single and MF homes throughout the whole area.  It's a definite time saver. 

@Daniel Wang pick up the phone and call a couple local property managers. Have a list of questions. Listen and learn. They have their pulse on the market at all times.

@Daniel Wang

You can use city-data.  You can look up almost any city and find demographic information.  It might be last years information, but it’s pretty accurate.  

@Brian Gerlach great idea!