Rates vary tremendously. My advice for a writer is not to sell yourself short. Get the experience you need and then go for the higher end work. There's not necessarily a going rate for the higher end work. There are so many factors that weigh in. For many authors, it will be more about what you are bringing to the table (including expertise and experience, but also things like how easy you are to work with, how flexible, how much fun!!) than about wether your rates are the absolute lowest.Having said that, you may need to spend some time "in the trenches" proving yourself to get the experience and references.If you are an author hiring a collaborator, perhaps ask references whether they felt they got their money's worth.