Resource for finding rental demand/vacancies in any market

[Will Randolph]

Hello there biggerpocketeans,

New to this goup, and was wanting to know what is the best online resource for finding how much the rental demand there is in any selected market, and how many vacancies there are, also average rental rates.  I know there has got to be a resource. and obviously I could google or toggle with Zillow and trulia, but there probably is an easier way, such a silly rookie I am.  Thank you for you assistance. 

-Will