Hi, 21-year-old college student here. I just got a fairly significant monetary gift and was wondering what I should do with it? Sidenote: if someone wants to explain why paying down your mortgage vs. putting that money in an investment account is the way to go. My theory is that 4%ish APR is still less than 7% averaged market returns so, therefore, you are forgoing 3% interest so there must be another factor at work here.