Co- writing with a celebrity

Does anyone know of resources for how to successfully pitch a book to a celebrity? Better yet, has anyone done this, and have tips to share?

I've completely written a book that's a perfect fit for someone's platform, and, I believe, culturally relevant, but I want to be sure I nail my pitch. All I need is the celebrity's name and platform to promote, and I hope to gain recognition for my own name. I realize this is shooting for the stars, lol. But if they agree, any tips for negotiating a contract? I don't have an agent, and I don't think they do either, so I'm pretty sure the project would be indie. What kind of royalties could I realistically expect to keep? I definitely don't want to be a ghost-writer.