 Notice the money's still there. You got the money's from the bank, typically. So guess what? The money keeps growing each year, every year, for the rest of your life. Compound. If you understand compound interest, you understand how one goes to two, two to four, four to eight, and eight to 16, and so on. So the longer you compound, the faster the money grows. Compound interest is considered the eighth wonder of the world. Sometimes I've heard that. If you pay the interest on the bank line, the interest on the loan, not the principal, just the interest,