how much debt

[Troy Forney]

I am getting ready to close on my 4th house within a year. I had a goal of 20 houses by age 50. I am 43 now. I have been moving forward pretty quickly acquiring good cash flow and equity. It suddenly occurred to me at 10 deals I will have $500,000. (Roughly) debt on these properties. I know they will be paid down some. If I am averaging 40% equity on each house, do I need to worry about the debt if I have positive cash flow?  Any advice? Just don't want to do much too fast.