Market Analysis for rental

[TJ Dittmar]

I'm a beginner and I'm looking for tips on how to perform a proper market analysis on houses to buy and hold long term and rent out.

Right now I'm looking through all the MLS websites and finding properties in locations and within my price range. Then I'm looking at the active comps in the area as well as what the market in that location has done over the past month. Then once I find a property that I like to buy I'll start looking at the comps in the area that have been rented and are currently on the market to be rented and make sure that my mortgage payment will at least break even with the rental comps.

I'm using rough estimates on Zillow and websites alike. The ones I'm very serious about I'll call and get a home owners quote and verify the current assessed taxes to give me a more accurate mortgage payment. 

Is there anything else is should be looking at? Formulas I should be using?
Pieces of information I'm missing?