A degree in engineering has always been a sure way of getting hefty pay packages in the previous century, irrespective of the particular stream. Engineers are the sculptors who have molded the modern day world out of rocks and sand. Even though specific trends in the demand of the particular type of engineering may vary - as is the case that if software engineers are in demand today, mechanical and civil engineers may be in demand tomorrow - it is presumable that the demand for a well-qualified engineer is never going to slow down.
Hence, it is not surprising that a significant fraction of the engineers work on a freelance basis, as is the case of most professions today, such journalism, architects, writers, and web designers, to cite a few examples. This is even truer for certain specific branches of engineering, such as software engineering, civil engineering, and bioengineering.
Government bodies and corporate bodies from different streams hunt for well-qualified engineers to undertake all sorts of projects. The ambit of projects might include almost anything, from constructing a model for making a car accident proof (production engineering), to smaller and faster bluetooth modules (electronic and communications engineering), to a 4-cylinder gasoline operated engine (automobile engineering) to a PLC program for mobile devices (software engineering) to the construction of a small bridge (civil engineering). The particular thread that connects all of these projects is all of them are short term, small-scale projects - perfect for a freelance engineer who likes to work on a contract basis without being associated with firms or companies in a long-term deal.
The duration of the contract for a freelance engineer may be anything from a few months to a few years - depending on his field of engineering and the specific project. The freelancers sidestep all the baggage of office life and relish their freedom of timings and the personal touch imparted to their job by the act of freelancing.
The companies on the other hand, strike deals at rates lower than corporate engineering firms and get almost as good service from the freelance engineers. The interaction between these two parties occur primarily through ads in papers, or more recently, via internet forums which provide a platform for companies to put up their projects and for freelance engineers to apply to them as per their wish. Even though this breeds a lot of competition amongst the freelancers, freelance engineers are a tough breed who has been persisting in a cutthroat market of other freelancers as well as corporate engineering firms.
However, freelancing is not as romantic as it may sound at first - freelancers have to bear the brunt of financial downturns, such as the one last year. Furthermore, a well-established company say something like Shell, might pay huge, obscene amounts to its top engineers, which might make one, think twice before leaving a top company for a freelance engineering career. Also, in freelancing one has to be always on one's toes, as projects do not just drop on your lap, you have to go and get them. Only by selecting smartly and wisely can freelance engineers hope to carve a notable career for themselves.
Freelancing, particularly in engineering, has several visible shortcomings at the outset - but any freelancer could tell you that they would never give up their freedom, and the liberty to work at will, for all the money in the world. It is this different set of priorities that make freelance engineers take the path that they take.