Since ``leverage'' is so often used as a synonym for debt, let's review how debt leverage works in a common financial transaction--buying a house. Suppose you want to buy a house as an investment, and that the house costs $100,000 (this is a hypothetical example, after all), and you can expect to get about $600 per month in rent from the house. Suppose you were fortunate enough to have the full $100,000 in savings and bought the house for cash. If you sold the house one year later for $110,000, you would have realised a total before-tax gain of $17,200 on your investment, the $10,000 appreciation in the value of the property, plus 12 months of rent at $600 per month. Dividing the proceeds by the investment, you would have realised a yield of 17.2% on your $100,000 capital.
Most people don't have $100,000 in the bank and even if they did, they wouldn't want to tie it up in one investment. Suppose, instead, you bought the house by making a $20,000 down payment and borrowed the balance of the purchase price, $80,000, by taking out a mortgage secured by the house. If mortgage rates were 12%, you'd be making payments of about $800 a month, but since those interest payments are tax-deductible you'd be able to cover them from the rental income. When you sold the house at the end of the year for $110,000, you'd end up with a gain of $10,000 (assuming the rent just covered the loan payments), or a gain of 50% on your investment of $20,000. If you'd had $100,000 with which to play the market, you could have bought five houses this way and wound up the year with a gain of $50,000 compared to the non-leveraged gain of $17,200.