Ask HN: Have you had any experience with ghostwriters?
Fiction or non-fiction, positive or negative?
I don't know whether my experience is relevant, but there it is.
If you are looking for a ghostwriter, ask your writers to submit MULTIPLE examples of their work and give the most detailed guidelines you can. Honestly, hiring a ghostwriter for your project will be difficult. You're going to need to put in the work to make sure that the writer's voice matches your needs, and your needs are in-line with what your writer can deliver. Communication is super important. Ask for early draft reviews to make sure you are on target and cancel the relationship early. Getting a terrible manuscript that you will need to re-write is worse than paying someone for a few hours of their time and cutting your losses.