I'm a freelance writer, and I have been for about ten years now. I've written on lots of different topics and in lots of different formats. I love to write.
While there is decent money to be made in freelance writing, it can take a while to find lucrative markets for your pieces. And there is no guarantee that you'll make money on a piece you've written.
With that said, if you enjoy writing there are many online resources for paid writing jobs. However, many of them are extremely low paying. Some pay less than a penny a word (which might be okay if you enjoy the topic and want to write about it for your own enjoyment). If you want to make money you certainly won't be able to make your living on those low paying pieces.
There are also many scams out there. You'll often find scams on Craigslist in the writing job section. If someone asks you to submit an original article so that they can see your writing style they may be planning on selling that article to an online content website for their own gain. There have been some people who've done this and then they bragged about it on "hacker" style websites. How conning an honest person is anything like computer hacking I'll never understand. I guess it makes them feel smart.
Anyway, here are some sites I've used (with varying degrees of success) to make money over the past several years:
Some popular sites that writers I know have also worked for include:
I'm sure that I will touch on freelance writing again, but I wanted to give an introduction to those who are interested but have no experience so far. I think the sites listed above are a good starting point for finding work online.
One more resource is Writer Beware. It's a great blog by experienced writers. It contains info about writing scams, signs to look for when working with a new company/agent, and a list of scammers with a track record of screwing writers out of work and/or pay. Here's the link: Writer Beware.