@Brian Lewis there are a ton of indicators that you can look at, and you named a few. However, and you mentioned it in your post, don't get paralyzed by your analysis. The objective of your rental strategy it sounds like is cashflow (you are specifically citing multifamily). Don't overthink it - determine what your return expectations are and start looking at specific properties and running the numbers. If it makes sense, dive in! You need to make sure that you know the area you are working in well (you can talk to people who work in the market) to make sure you aren't buying in bad pockets, but there are tons of investors working in many of these large cities already, so there must be some upside to it.
Atlanta, for example, is a great city that still has great returns when compared to other major markets. Just like other cities, you need to be careful as the city is block by block and street by street. However, tons of institutional money is being pumped into the city, and those guys are doing there homework!
Give me a shout if you'd like to talk about the Atlanta market. I'd be happy to chat through it / multifamily with you.
Mike