Borrow $70k at beginning of the year, pay 5% interest, your Pre-tax income is $70k. Make loan repayments monthly, all of it tax-exempt. Where your original post

Borrow $70k at beginning of the year, pay 5% interest, your Pre-tax income is $70k. Make loan repayments monthly, all of it tax-exempt. Where your original post-tax income is $50k, your post-interest income now $67k. Spend the $70k minus interest as tax-free money.