Given the diverse range of economical backgrounds coders come from for Rentacoder projects, Making being undercut quite a common occurrence, your looking at $15-20USD per hour on a run of the mill job, Providing you have decent enough ratings and offer a decent comment to show your competence and experience.

Personally I prefer to have no more than 3 projects happening at any one time, But its a risky job to have as your primary income, So you take what you get, when you get.

Its definately a great place for making some quick cash on the side. And I've always enjoyed being able to have a bash at new challenges I might not find elsewhere.