I have often spoken with entrepreneurs and investors about how they identify good business opportunities. This discussion usually leads to a list of characteristics that separate profitable businesses from unprofitable ones.

In some sense, everyone is an entrepreneur; that is, everyone has a career.

I believe that the characteristics of good business opportunities can also be used to evaluate careers. For example, the first characteristic of a good business - or career - is a long-term, sustained demand for the service or product. Fad items such as pet rocks or hula hoops may seem appealing for a time, but the long-term demand is not sufficient to warrant the large up-front investment that is required. Similarly, it is a good idea to choose a career that has a long-term, sustained demand rather than chase short-term opportunities that come and go.

The second characteristic of a good business is one for which there are few competitors. Some of the most profitable businesses I've seen are those that specialize in a niche product that has few if any competitive producers. Similarly, some of the highest-paid doctors are those who have become the regional specialist in a particular ailment.

Try to specialize in an area in which you become the expert and the niche is not big enough to warrant a lot of competition. This may mean that you accept assignments that are on the edge of your knowledge and that force you to develop new skills.

The third characteristic is a business that has a stable technology that will not likely be displaced by new and superior technology. There is not a lot of demand today for slide rules, buggy whips or whale oil lamps. The same is true for career decisions. The demand for travel agents, for example, has plunged since the advent of online booking.

Try to learn skills that will not be displaced by new technologies. This usually means a lifetime of learning. Accountants were among the most easily placed students from the business school this year because they understand the rules that have recently changed. The fact that accounting rules are constantly changing means that accountants must constantly update their skills. Businesses and individuals must keep a constant eye on changing technology to ensure their product or skill is not becoming obsolete.

A fourth characteristic is a barrier to entry. If just anyone can get into the business, profitability deteriorates. My students are often surprised to find that there are so many new entrants into the highly unprofitable airline business. One reason is that the barriers to entry are so low. A new entrant in the airline industry does not even need routes. New entrants can make money until they become larger and face the same problems as the majors. Meanwhile, all the players suffer from the intense competition from lower-cost new entrants.

Similarly, if just anyone can perform a task, the wages are usually not very high. Clerks, workers at fast-food outlets, janitors and other employees will likely never be paid much above minimum wage. If retail operations paid higher salaries than their competitors, they would have to charge higher prices and would eventually lose customers to lower-cost competitors.

There are, of course, other characteristics of entrepreneurship that would be similar to having another career. But there is one key difference. For a business to survive, it must be profitable. In another type of career, however, many people do what they love even if it means that they don't have much income. Still, if you can do what you love and still meet these criteria, then your career - or business - can also be financially rewarding.