By aggressively trading on margin he can produce 5% daily profits on the 100k buying power he will grow their 25k cash at the rate of 20% per day. The risk of course is that he will make a mistake that will cost him everything. Unfortunately, this is the fate of 9 out of 10 traders. The cause of these career ending mistakes is a failure to manage risk.
Scalping can be very profitable for traders who decide to use it as a primary strategy, or even those who use it to supplement other types of trading. Adhering to the strict exit strategy is the key to making small profits compound into large gains. The brief amount of market exposure and the frequency of small moves are key attributes that are the reasons why this strategy is popular among many types of traders.
The common use of buying on margin (using borrowed funds) amplifies gains and losses, such that substantial losses or gains can occur in a very short period of time. In addition, brokers usually allow bigger margin for day traders. In the United States for example, while the initial margin required to hold a stock position overnight are 50% of the stock's value due to Regulation T, many brokers allow pattern day trader accounts to use levels as low as 25% for intraday purchases. This means a day trader with the legal minimum $25,000 in his account can buy $100,000 (4x leverage) worth of stock during the day, as long as half of those positions are exited before the market close. Because of the high risk of margin use, and of other day trading practices, a day trader will often have to exit a losing position very quickly, in order to prevent a greater, unacceptable loss, or even a disastrous loss, much larger than her original investment, or even larger than her total assets.
Day trading is not for everyone and involves significant risks. Moreover, it requires an in-depth understanding of how the markets work and various strategies for profiting in the short term. While we remember the success stories of those who struck it rich as a day trader, remember that most do not—many will fizzle out and many will just barely stay afloat. Furthermore, don't underestimate the role that luck and good timing play—while skill is certainly an element, a rout of bad luck can sink even the most experienced day trader.
Successful traders have to move fast, but they don't have to think fast. Why? Because they've developed a trading strategy in advance, along with the discipline to stick to that strategy. It is important to follow your formula closely rather than try to chase profits. Don't let your emotions get the best of you and abandon your strategy. There's a mantra among day traders: "Plan your trade and trade your plan."