 So it works. During tax time, if you have a mortgaged home, you can deduct the interest of your mortgage from your tax bill. You can do this on your first home and your second home, including your yacht or your ski cabin or your RV. And that cost us about $26 billion a year. In a few years, because the expiration of some caps that Trump put on with his tax bill, it's going to cost us over $100 billion a year. Okay? This deduction.