Though I don't promote using Demand Media Studios (also known as Demand Studios and DS) as a full-time gig, it is great for when your freelance assignments are at a trickle. That's what I've been using it for over the past few years.
The trick to making decent DS income is to find titles quickly and write them quickly. Here are some of my tips:

Make use of the "Save Searches" function. Choose what format you like and the rate, then use a certain keyword to find titles and save it. You can save up to 20 searches. This saves time because you can just click a link to bring up a previous search instead of ticking boxes and typing out keywords. Focus on only one or two formats. I only do how-tos. I've gotten so good at them I can whip through one in about 15-20 minutes, including research. That's around $60 an hour. Stick with subjects you know a lot about. This reduces your research time. I stick with video games, fine art and crafts. Some keywords I use to search for these articles are "watercolor," "yarn," and "Pokemon." Stick with subjects that you have reference books for. I almost only use books that I have on-hand as references. A CE can't argue with the validity of a book's advice and I don't have to fight with Google to find a website reference that isn't on the blacklist.  Be nice to the CEs. Say please. Say thank you. Let them know that your article is a little short because you didn't want to fill it with fluff. Tell them why you think you qualify as a reference, don't just assume they'll notice it in your bio. If you think explaining why you make a good reference takes to much time, create a boilerplate explanation that you can copy-and-past into the comments section. Here's what I use on art articles: "Additional Reference: As noted in my bio, I have over 20 years experience as a professional artists. Thanks!"