Thoughts about what to do with cash flow, reinvestment and growth

[Chris Armstrong]

I just want to get the perspective of some folks who have a little more experience in this area than I do, I would love to know the other perspectives that I am not seeing. One of my favorite quotes is " you don't know what you don't know" so lets see what the consensus is. 

I have 3 properties at the moment. One is completely paid off, the other two have mortgages on them. I generate significant cash flow per month ($2000+ per house) after all expenses. My ability to borrow money is very limited right now (~$100k) because of the amount of money I make at my W-2 job and my current debt load. I owe a total of $210K on the other two properties.  Currently I am taking the extra cash flow and plowing it back into the mortgages to pay them down as quickly as possible and I should be done and own all three within four years. I literally do not take $0.01 from the business right now.  My question is, is this the best approach to building a portfolio? 

I know I could cash out refinance the property that is owned outright or get HELOCs, there are many things I could do. I just want to know what others in this situation have done and their thoughts. Thanks