How much monthly cash flow should you get on a rental property?

[Dr. Jordan E Smith]

I have been reading a lot of books on rental property investments and have heard varying opinions on what qualifies as a "good" rental property investment based on monthly cash flow. 

I've read anywhere from $80 to $600 net monthly cash flow. I am in the north Georgia region and realize there are varying expenses based on region. 

For any experienced rental property owners: Obviously more is better, but do you have a minimum monthly cash flow amount that you require in order to purchase a property?  If so, what is this figure for you? 

Thanks so much for any feedback.