Regarding "ghost writers". A ghost writer is someone who writes in another person's name. For instance, a newspaper might think it's great to have a famous person write a regular column. But the famous person can't string words together. So a skilled journalist does the writing for him, usually in secrecy. It's this mysterious, secret element that earns this task the title of "ghost writer". I've been a ghost writer for some famous people, including John Laws. While it's fun putting words in another person's mouth, it's also a big responsibility to understand the person's way of thinking and expressing him/herself.
The skill in ghost writing is not really writing at all. It is listening. Your own style, the voice you have spent years building, has to disappear completely, and the other person's voice has to come through so naturally that their own mother would swear they wrote it. That means studying how they talk: their favourite words, the jokes they tell, the things they would never say, the rhythm of their speech. You are an actor as much as a writer, playing a part on the page.
It is honest work, despite the secrecy, and it is everywhere once you know to look. A great many celebrity columns, autobiographies, speeches and "as told to" features are the work of an unnamed professional. The famous name has the life and the standing; the ghost has the craft to turn it into readable words. Both bring something real to the deal.
Two rules will keep you safe in it. First, get the arrangement clear and in writing before you start, so there is no argument later about money or about whose name goes on top. Second, never put a word in your subject's mouth that they would not stand behind, because when it is printed, they are the one who must answer for it. Serve their voice faithfully, and keep your own ego in the drawer. That is the whole art of it.