You should be aware of a few disadvantages to this trading method before you start. First, since it allows you to control a larger position than your actual investment, it also amplifies your losses if the trade goes against you.
Second, most brokers will require you to maintain a minimum balance in your account (known as the margin requirement). If the value of your account falls below this level, your broker may ask you to deposit more money or close out your position. Lastly, the fees associated with your margin account can eat into your profits.