I have used freelance.com in the past, but from the time I spent there, it is a lot more competitive and freelance.com takes fees for almost anything (for placing a sponsored bid, taking a skill test, to withdraw money etc.)
I have had much greater success through Upwork, in my opinion it is better than freelancer, there is a fixed fee that you pay Upwork for money earned by a single client, you have payment protection as long as you follow the rules, so that means even if a client plays it dirty, you are still guaranteed to earn the original amount that you have agreed upon (read the about fixed price protection carefully). The fee is not too bad and is simple to follow:
20% for first $500
10% after >$500
5% after >$10,000
The fee is calculated by lifetime earnings from a single client, so if you have a long-term client who has paid more than $10,000 for your services, then you only cut 5% of the following earnings to Upwork.
It depends on what your client is looking for, and if they are a programmer and are wanting to deal with the script. If you are having a hard time with a task, then I do recommend planning out what you need and make sure that your requirements are clear before approaching a freelancer. Upwork also offers client payment protection, so as long as the requirements are clear, you should be on the safe side, even if the freelancer does not have a good will.
From my personal experience, I am working with a client who has very good understanding of all programming concepts and has worked on many complex software projects, but they instead chose to focus on their business instead of the intricacies in programming (which can often get overwhelming, especially when you are running a business alongside). So at the moment I am taking care of all the code while my client takes care of testing and the higher level design of the code
I do not think many do actually, most of them do it as a hobby or as part of their already existing traditional job. There are a few I know who do take up freelance work now and then, I am one of them myself (if you haven't figured out that by now ). From on top of my head, both @Xandy and @Danyfirex are open to freelance work, not sure I remember any other members who are know to work freelance.
It is actually not that hard to become one, as long as you have the right skill and knowledge, you can utilize it to work on related jobs. Always be persistent when looking for jobs, especially in the beginning. It might not pay your bills until a few months, as your reputation on the site grows (ratings, client feedback, ranking/status), you will start getting a lot more jobs, enough to make a living if you plan it out just right. It might be worth trying this if you are not living independently and have someone who can take care of your expenses until you get on your feet.