At least double or nothing

[Mitchell Cord Cantrell]

I was given a piece of advice that really makes sense to me but I thought I would get some other opinions on the idea.

The advice is that if you are going to buy any form of real estate to rent out you should, at the bare minimum, be getting twice the amount a month in rent than what it costs you to own and operate it or don’t buy it. 

So I guess my question is; is this a good foundation to go by and if not then what would be a good ratio?