Used sensibly and moderately, Mr. Margin Account can be a good source of fast loans. But used poorly, Mr. Margin Account can leave a smoking hole in the middle of your portfolio. A margin loan is a loan against the securities in your portfolio. Naturally, you'll have to pay interest. Just how much depends on the broker's base rate, sometimes called the call rate, and the size of your balances.
Larger accounts pay less.
Most people borrow to buy more stocks, which can amplify your gains. For example, suppose it's March 15, 1999. Unfortunately, margin also magnifies your losses. Suppose you decided to take the plunge in Intel on March 20, 2000. If you didn't, your broker would have sold the stocks in the account to pay off the loan.