Miley Cyrus made $18.2 million in 2007 through her Hannah Montana franchise, and she may make more in 2008 now that she's adding 'memoirist' to her list of talents. Disney Book Publishing (DIS) announced this week that the tween queen signed a seven figure deal to pen a memoir. Sure, she's only 15, but according to her publisher, she's still got plenty of material to fill a book.

"Miley will share her inspiring story, spanning from her Southern roots in Tennessee to the excitement of her record-setting triumphs in TV, music and film," the Disney Book Group said in a statement. "Notably, Miley will reveal how her solid relationship with her family, especially her mother Leticia, helps her navigate the spotlight and encourages her to contribute and connect to the world in a variety of ways and grow up happy and well-rounded."

One thing Cyrus should consider before putting pen to paper is enlisting the help of a ghostwriter. According the The Penn Group, a New York based ghostwriting firm, celebrities utilize more ghostwriters than the rest of the entire book and newspaper industry combined. "By my conservative estimate, I'd say [celebrity ghost writing] happens most of the time," says Sarah King, executive vice president of ghost writing at the Penn Group. "I have every faith and confidence in Miley Cyrus's intellect, but between filming the TV show and being Hannah Montana, I think she has a lot on her plate and it's pretty clear there'd be a ghost writer involved."

But ghostwriters aren't only for the Hollywood elite, and they're not only used for books. Anyone with a story can use a ghostwriter, whether it's a company president, a doctor, or a corporate professional writing sales letters or speeches. "A lot of the time the folks who use ghost writers are leaders in their fields," says King. "And a lot of our clients are also folks who have just dreamt of a book for years and believe their story should be told. Whether it's on their own lives, or a novel or a screenplay, they might not know how to structure a book, or put words down on a page."

Think your life story could make salacious beach reading? If you don't have time to write it yourself, make sure you have some extra cash. Depending on the complexity of the project, a ghostwriter will typically cost between $15,000 and $40,000. "Obviously a writer who is nominated for a Pulitzer or has a Times (NYT) bestseller might charge more than a writer at the lower end of the price range," says King. According to the Penn Group's website, best selling and celebrity authors demand between $50,000 and $250,000.

And hiring a ghostwriter doesn't absolve you from putting in some serious effort. "Most people think, 'okay I'll hire someone and they'll do all the work for me and I'll tell them my story,'" says Julie Ann Shapiro, an independent ghost writer based in Encinitas, Calif. "At the very minimum, outline what you want to say. Otherwise it will take hours and hours to extract that information and it's not cost-effective." Also, make sure the writer is contracted as "work for hire" to ensure you are entitled to whatever profits or royalties are generated by the book.

Cyrus's memoir is slated to hit shelves in spring 2009, just in time for The Hannah Montana Movie. And if Cyrus just can't find the time to write the book on her own, she won't be the first. "There are a few [books] out there that I'd say were written by the actual celebrities," says King. "Bob Dylan's [Chronicles] is the only one I can think of. But I just can't imagine Nicole Richie sitting down at her MacBook (AAPL) and working on the fourth draft of the third chapter in The Truth About Diamonds" (NWS).