A ghostwriter is a professional possessing literary expertise that writes on behalf of someone else and gets paid for it.
In a nutshell, a ghostwriter is a writer who will help you write a book for you and give you complete credit for it and against that he charges for his service
Yes, It is legal to hire someone for your book.
You can if you have the written approval of those individuals involve in your life but if you don’t have that, then it is better if you use pseudo names and change the name of places so you won’t be violating someone’s privacy.
In line editing your editor will be looking into spellings and grammar while a developmental editor will help you with these services a long with sentence and story structural assistance.
There is only ONE key difference: If the author owns the rights and royalties, then the book is self-published. If the publishing company owns the rights and royalties, then the book is traditionally published.