<prompt> Human: New homeowner here 26Northern VA! I just made the second mortgage payment of my life and have been trying to figure out if I should be paying extra towards principal every month. I understand the long term snowball benefits of paying off the mortgage quicker as well as the tons of interest saved over the life of the loan. However, I have a 30 year loan at 4.125 and Im planning to live in my first home for up to 10 years.. maybe 15 years depending where life goes kids, jobs, etc.I consider myself an extremely fortunate individual raised by financially responsible parents who have taught me well. I carry no debt so the alternative to principal payments is putting the majority of money into a brokerage account to invest in index funds.. What are your opinions on paying additional principal in this case?  <response>: Here are some made up numbers to illustrate. If your initial balance is 250,000, after 10 years of making your regular payment you will have paid 93k in interest and you will still owe 198k. If you pay an extra 100 per month you, after 10 years you will have paid 90k in interest and you will owe 183k on your mortgage. Paying in an extra 12k saves you 3k in interest and 15k in principal. You can figure out roughly how much money youll save in Excel by typing in FV.0412512, 120, your extra monthly payment here, 0,0Good luck! 