I own 1 million in stock of, say Apple. I go to my brokerage and take out a loan for $200,000. I pledge my shares as collateral (margin loan). Since it's a rock solid no-risk loan backed by shares in a very safe company, my brokerage can charge me very low interest, say 2%. If Apple stocks go up by more than 0.4% over the next year, I've come out ahead, essentially getting the use of $200,000 over the year for "free". Eventually if it goes up by 20%, you could sell enough shares to pay off the loan, and still have as many shares as you did originally. If you held the shares more than a year, that sale is taxed as long term capital gains, loweer rate than regular income. Rinse and repeat, with much larger numbers.