I've used elance (many years ago) to pick up extra part-time work and that worked out well. However, my general feeling these days is something like, I am paid pretty well at my day job already so I want to do fun things in my time outside of work. Others may be in a different position where they want to work for themselves here and there, but the people I know who do this tend to establish a client base that comes back for repeat work pretty quickly and then they don't go looking for new stuff any more.