<prompt> Human: My husband and I bought our first house last year. Its a 30 year mortgage at 4.25 interest, but weve been paying an extra 650 toward the principal each month.We plan to live in this house for at least 5-10 years, but we like the idea of keeping it as a rental property after that. We live in a college town and rental houses do really well around here. Would it make more sense for us to instead use that extra 650 a month to start saving up for our next house, instead of paying down our mortgage? Are there any other factors we should be considering?  <response>: Your mortgage rate is low, and is fixed. Stay in the house and invest the 650mo in low cost index funds. You will make more on the investment than paying down the mortgage. Unless your market is real hot, selling in a short time will bet a loss. If your market is hot, the likely capital gains will go to pay an inflated price on the next home.Tldr: invest your money in low cost index fund instead of paying off a mortgage early. 