How do you calculate Cashflow and out-of-pocket

[Jin Zhang]

I've seen several posts talking about having a positive cashflow using the Rent minus All Expenses calculation. Personally I find it hard to imagine I'd be out of pocket $8,000 a year even knowing the rent is paying $8k to 9k in principal  (which is not an expense), leaving me a positive cashflow (but I could only realize it when I sell above certain price). If I'm out of pocket only a couple of grand a year (still with a positive cash flow on paper) then I'd feel more comfortable and resilient, but the numbers I give above aren't that far-fetched in the hot market today even putting 20% down. 

What are your take on this when you evaluate a potential investment property? Am I just out of touch with the reality, not looking in the right area or the right types of properties?