return on cash flow property question

[John Voychick]

I'm been looking through the site and am having a little trouble finding what I'm looking for.

Basically I'm looking at a property for 67k renting for 760/month

The TK company claims $408 in cash flow but that doesn't account 10% for PM, maintenance, vacancy [although they have a 3.5y average], rainy day fund, and other operating expenses.

Can someone point me in the right direction or suggest what they use? I find that the calculators ask me for numbers and percentages that I do not know just yet as I am new to this.

Thanks in advance!

John