It is wise to start your search from within ghostwriting communities or forums where writers connect directly with clients. Reedsy and other websites could guide you to the right person, considering that different ghostwriters more or less specialize in fiction, memoirs, business guides, and self-help.
First, you must be clear about your project: some outline of the general idea of your book, your target audience, and the approximate length before you hire any ghostwriter. A professional ghostwriter will require this information before he or she submits a quote and timeline.
While the top ghostwriters expect much more, there are tricks to cut costs. For instance, some writers will offer a payment plan, in which you pay by the chapter or according to various milestones. Other options could include working with a less experienced ghostwriter—someone just starting to build his or her portfolio and willing to borrow their rate by offering lower-quality work.
Also, remember to always ask for samples of their work, and consider requesting a small paid trial. For example, have them write a sample chapter based on your outline. This gives you an idea of whether they can match your voice before you commit.
Yet another option would have to be the more integral collaboration. You could discuss your ideas and shape some of the main integration of the book, while a ghostwriter makes it coherent, editing and finishing it. The outsourced completion could save some time and money, all the while bringing about a relevant finish.
Finding the elusive perfect ghostwriter can take time, but after that, they're the ones who'll shape your story into a publishable work.