Don't borrow money to use for stock market investment. On the stock exchange, borrowed money is known as either gearing or leverage. It is typically used either by companies (to help them finance growth), investment banks and hedge funds (to help juice their returns) or very aggressive traders. There are many spread betting (information here), options trading and day trading strategies that use borrowed money to enhance returns, but it also has a very profound impact on the risks being taken with each trade.
You're probably looking for deals and low prices, but stay away from penny stocks. These stocks are often illiquid, and chances of hitting a jackpot are often bleak. Many stocks trading under $5 a share become de-listed from major stock exchanges and are only tradable over-the-counter (OTC). Unless you see a real opportunity and have done your research, stay clear of these.

One constant principle of investing is that markets fluctuate. Stock prices will rise and fall for a number of reasons: the economy, investor sentiment, political uncertainty at home or abroad, energy or weather problems, or even corporate scandals. This means market performance isn’t always predictable. That is why diversification, or spreading the investments in your portfolio among different asset classes and across different sectors within each class, is such an important strategy. Diversification is a time-tested way to manage risk.
If there are any lessons to be learned from the American sub-prime mortgage crisis, the 2008 stock market crash (information here) and Wall Street bailout that followed - and there are lots of lessons - it is that borrowed money can be very dangerous in investments, even when it is being handled professionally. The failure of LTCM, Bear Stearns, Lehman Brothers, Northern Rock and many others shows just how precarious a business model can be with too much gearing. 

You’ll come across an overwhelming amount of information as you screen potential business partners. But it’s easier to home in on the right stuff when wearing a “business buyer” hat. You want to know how this company operates, its place in the overall industry, its competitors, its long-term prospects and whether it brings something new to the portfolio of businesses you already own.
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