The benefits of staring your own blog or writing for blogs that promise revenue sharing both have their advantages and disadvantages.
Starting a own blog gives you full control over the content, and raises the possibility to earning maximum revenue through Google AdSense and other avenues. However, on the flip side marketing this blog and attracting visitors to visit your blog on a regular basis is a major challenge and the stumbling block for most writers.
Joining a popular community blogging service that provides for revenue sharing, either by sharing google adsense revenue, or through a fixed upfront fee or fee for number of visitors would be a solution. The writer can concentrate on generating good quality articles and leave the marketing aspects to the blog owners. The lesser revenue would definitely be made up by more visitors to such blogs.
The major point to consider in the latter case is to ensure that the blog you join is reliable and has a history of making prompt payments.