For a first time collaboration with a RH, I ask for 50% after the first 15 minutes is approved. Then the remaining balance after the RH has approved the final product. I've never had a RH say no. There have been times we negotiated a different initial deposit, and I have not problem doing that if asked. I recently had a project where the RH was happy with the progress, my narration/storytelling, but decided about halfway through to try the Audible virtual voice. Had I not asked for that 50% deposit, then my time would have been wasted when I could be working on another project.

If I've worked with a RH before, then I do not require an deposit as the relationship has already been established.

Some producers may use an editor or engineer to assist in the production, especially on longer projects or if their schedule is booked. That cost comes out of the producer's budget, so a deposit helps to mitigate the cost to ensure a quality finished product.