Rental Calculator Question

[Scott Boddicker]

Looking to purchase rental properties in and around New Braunfels, TX.  Been listening to the podcast and seems like the big rule is to make $150+ a month per unit after all expenses (mgmt, repairs,vacancy,etc).  I'm confused because you can achieve this positive cash flow or great based on your amount of down payment.  Am I assuming a 20% down payment, no-or very low down payment, can anyone shed light on this for me?  

Thanks,
Scott