It's very rare for you to have just one marketable skill. You will most probably have many. Take me for instance, I'm great at fixing computer issues; I'm almost perfect at MS Excel; I'm good at Network Administration (both Voice and Data); I just recently got a trial job as a Finance Analyst after passing a rigorous Finance and Accounting test by a Dubai based start-up; I blog and make some money of it; and I'm a business intelligence analyst (that's what my CV title reads). So career-wise, I've got lots of options. Early last year, I went for a job interview at a Financial Solutions company. I have no finance background and no finance work experience. I didn't get the job, but they were very impressed. The big issue was, as one of my interviewers said, some things can't be learned from books and they needed an experienced hire. Then 4 days ago, I got a job invitation to be a Valuation (Finance) Analyst for a Dubai based start-up firm. It's going to be a work from home job, and part-time too. They were interested in just one thing -- the right knowledge, which comes from books only. So this time I was lucky, I passed the rigorous 5 hours test that covered Use of English, Data Analysis, Excel, Finance, Accounting and Valuation. I'm on a one week trial job. If I pass that, I might get the job. And that's what the world is turning to. If you are good enough at a thing/skill, your educational qualification is not going to matter. Just prove your expertise and show your track-record. I know a guy who gets juicy part-time (contract) jobs from big companies like Oracle and earns over a million naira per month without a University degree. His track record speaks for him.
For most of us, the real trouble is knowing/choosing the skill to focus on and market aggressively.
So how do you figure out what to focus on?
Over 200 years of economic research has helped with the answer. It says you'll probably have lots of comparative advantages, but you should focus on your biggest comparative advantage.
Let me break it down.
Every skill that has earned you money did so because you have a comparative advantage in it. Someone was willing to pay you because your skill level and pay demand gave you an advantage over the other offers/applicants he could find. I have been paid for programming jobs, photography, Business Data Analysis, Networking, Linux Training, Data Entry and Teaching Mathematics. So they're my comparative advantages. People have been willing to pay me to offer those services, because they preferred my skill level and charge to other people's. And that's how you figure out your comparative advantages. You could add skills you've not charged anyone for yet.
Of all my comparative advantages, I'm focusing on Business Data Analysis. Why? It's because it's the one that I can charge the highest for and I face the littlest competition for. Though some programming jobs have promised me very high pay; the competition is fierce and the cost of being up-to-date is very high. But for Business Data Analysis, the pay is not bad; the tools I use do not change radically every year; and there is very little competition. It's my biggest comparative advantage. And I focus on it. I keep building a track record, a market-place reputation. I want to be synonymous with Business Data Analysis. So, I turn down offers to teach Linux, offers to do data entry, networking job offers, and the temptation to become a professional photographer. I focus on my biggest comparative advantage.
For some of you, the path might be different. Maybe, unlike me, you've not tested the waters as regarding all the skills you could make money from, and you are not sure which your biggest comparative advantage would be. The easiest way is to stick to what you're doing now and be extremely good at it. Avoid drastic career change, except you hate your current career. Avoid starting all over too often. Stick to a career path and build your advantage in it.