What would be the best State/City to buy rental properties

[Oleg Serdyuk]

Hello, I am new to real estate investing. 

I live in San Diego, CA. 

My friend and I are planning to acquire rental properties somewhere outside of California. 

My question is: How to find the best place (State, city) right now in order to find great deals ? 

What are the main criteria we should look for, like the economy, employment etc?

Would you recommend reliable source to find this information? I am sure the data is available somewhere, but I am not sure where. 

Thank you