Good thing that there are only a few people who know that you prepaid your own mortgage. I mean, money is anything you want it to be. Barter is simply trading a lot of different kinds of private money for other kinds of private money. Federal Reserve Notes are simply public money that everyone has to recognize. --- Your mortgage promissory note is private money that you create when you sign it. Banks trade public FRNs for your private mortgage note money. Then they sell your note on the open market, usually for less than the face value, because they know that you will pay them a second time over the next 30 years. So, they make a bunch of free money. You pay twice, plus interest for nothing, plus the devaluation of money in general.