do I used extra cashflow to pay rental off faster, or reinvest it

[Thomas Harris]

I am currently in the car business, 20 years old and just closed on my first house, I am not looking to live off of the cash flow from the property, just wanting to build a portfolio, im currently making a 100k net a year so I can use part of that to reinvest in both cars and houses, the house I just closed on is a 15 year note with $450 mortgage, it is a 4 bed 2 bath and is basically rent ready, I have some people already interested in renting at $1100, my question is do I take the cashflow and pay toward the note and pay off in 8-10 years instead of 15, or do I use the cashflow to reinvest?