You should become a manuscript or book author's ghost writer, copy editor and proof reader. However, if you're only starting to think about a writing career, I suggest you get a bachelor's degree in English or whatever language; perhaps in language studies, English literature, creative writing, or English in general. A master's degree or higher is even better. I myself have a combined degree in journalism, fine arts and creative writing.
Once you have that, you need to get some experience. You could be hired by literary magazines, especially at your school, or you could write articles for newspapers, perhaps starting your own column. You can also acquire writing jobs on the Internet by looking up work. I suggest avoiding the low paying bidding jobs and going for regular posted work at sites like Daylo, or other freelancer's sites - where writing work is posted for free.
Once you have a few writing credits, you can begin your ghost writing career. I would suggest trying to get hired by a book ghost writers service, as there are many on the Internet. Another possibility is you can start your own service, as I did; mine is called Rainbow Writing, Inc., and we hire people who either have a lot of professional experience, a good educational background, and/or show a lot of writing talent. I have over thirty years of experience at writing, especially as a book ghost writer, copy editor and proof reader.
Once you get on the Internet, you will need to search engine optimize your website, post lots of articles with your credit box attached to them, or hire pay per click or other services to get advertising exposure. Then you can begin to acquire clients. You may start by offering a free five to ten page rewrite of a chapter the client sends you; this is what is generally expected of a book ghost writer and copy editor. You can quote a price, and I would start fairly low early on in your career, unless you have prior writing experience. Ask the client what he or she can afford, but stay reasonable, so you can keep your costs low and pay your bills.
As book ghost writers, copy editors and proof readers, we all need to make sure our clients are satisfied with their results. So while you are in the writing field, make sure you read copiously and on a regular basis, write short stories, poems and articles on a regular basis to refresh your writing skills, and be sure to work on a novel or two of your own. This will keep you handy when it comes to being a book writer for others as well. Another possibility is to keep a daily hardbound journal of your writing or simply comment on your daily activities, thoughts and dreams. This sort of thing can keep you really practices; I kept such a journal for over twenty years.
As to scheduling, it's a good idea to take on as many clients as you can handle. Don't overload, but you'd be surprised how much work you can do once you get into the swing of it. Try to get a book ghost writer job done in two to three months. If you charge $5000 per book at first, you can make $20,000-30,000 a year if you keep up on a regular basis. Once you have more experience, you can begin charging more money.
When you are a book author, ghost writer, copy editor and proof reader, you will find you are working a job that really consumes your time, so make sure you take the time to perform your other daily activities of family life, and set aside a one hour period every day to exercise. Book writers are one group of people who have the "sedentary lifestyle pattern" hazard, so in order to avoid getting sick, you must exercise. If you don't want to go outside and walk, purchase a cheap treadmill. Those work quite well.
Book authors, ghost writers, copy editors and proof readers all need to maintain the standards of our profession. When you are a ghost writer of any kind, chances are you won't be allowed to take credit for your work. It's supposed to belong to the works true "author," who is the person paying you to do the ghost writing. Even if you do most or all of the work, your client is the author of it and is the one who receive the credit, unless you make some other arrangement. If the client is willing, you can be coauthors with him or her, or make some other such arrangement, such as you getting credit and a percentage of book sales in lieu of upfront payment.
By the way – the method of payment for a manuscript or book ghost writer is upfront. You get paid in advance, in installments usually as the book is being written. This is the main advantage of being a book or manuscript ghost writer, copy editor and proof reader – upfront payment. You need to sound the client out on his or her budget, set a total price, and then ask for the first installment payment once you have been hired.
You might also sign a contract with a non disclosure clause with the client. The contract might be three way, if you are working for a ghost writing agency, or two way, if it's just you and the client signing it. A non disclosure clause states that you won't discuss the book's contents with anyone not designated by the client as someone with whom you may do so. Also, copyright laws in the USA and several other countries treatied with the USA, such as England, Canada and Australia, state that the author of the ghost written work retains full copyrights. You can check with the US Copyrights Office on the Internet to read the full scope of these laws.
Basically, even if you write the whole work yourself from research and you get nothing but basic ideas for the book from the supposed "author," he or she is still considered the true author of any such ghost written book, and will still hold full copyrights to all original material within it. This is, however, subject to whatever agreements you and the client make.
After the job is proof read, paid for and delivered, ask for a reference, also asking the client if it's okay to run an installment from the work on your website - with a credit that you are the ghost writer. Also, when the book is published, ask the client to include a reference to your name, perhaps within the Acknowledgements, as the book ghost writer.
You also don't have to stop as just the manuscript or book ghost writer. You may also be able to help your client set up to get his or her book published. This largely involves contacting literary agents and publishers. I would suggest contacting small publishing houses, and not the larger ones, unless you have a celebrity client with a large scale best seller on your hands. Due to confidentiality issues and ethical issues, you can't maintain contact with literary agents and publishers on a regular basis, but you can acquire lists of these people in order to contact them. Some more disreputable manuscript and book ghost writers also set up deals with literary agents and publishers where they are sent clients' work that the agents and publishers were sent, in order to edit it for them. Under the table money is made this way. It's not considered to be ethical practice.
It's satisfying to complete a client's book manuscript and then find him or her an agent and/or publisher. You can get a percentage of book sales this way, or by negotiating a deal with the book's author while you are being the book ghost writer. Sometimes a client will want you to work "on spec;" instead of paying you in advance, they will ask you to take a percentage of the book's profits. Unless you're sure the book is going to sell broadly, it's not advisable to do this, or you could end up working for free. But once you've got a book publisher's attention, anything is possible.
Lastly, be sure and enjoy your new career. Writing can be a fulfilling line of work, so if you keep at it, you can have tons of fun working for authors, getting the first time one's books written and published, and in general, having a "blast" as a book author, book writer, ghost writer, copy editor, and proof reader.
Get out there, now – and write!