Many ghostwriters (and all ghostwriting companies) charge a flat project fee. I have found that a flat monthly fee saves clients money since, while it is possible to estimate the time necessary to complete a work, a writer can’t precisely determine how long a project will take—unless he or she is going to rush through a manuscript. Basically you are paying for the professional time of a professional writer. What if a writer finishes your book ahead of schedule?
I work for a flat monthly fee so that you pay only for the actual professional time I spend on your manuscript. At the end of a project, work is pro-rated by the week (and day) if necessary so that you don’t pay for a full month if such payment isn’t warranted.