Their are varying levels of time, if you had a ghostwriter it would not be nearly as much of a strain on you as far as time goes it would just require a lot of work done before the writing started and then you would get chapters and regular updates from whoever the writer was. You would go over it with them and then you would be fine.

Writing is such a long drawn out process though it took me nearly 300 hours over about 6 months for my screenplay after revisions and all that were through like I said it was completely exhausting. You can move at a moderate pace, a chapter a week and for a 20 chapter book that isn't terribly long and a chapter a week definitely isn't hard to accomplish. It's on the backend that takes up so much time, the revisions and all that but as long as you odn't have a deal with deadlines in place, if you're just looking to sell your book after it's finished to a publisher then some time is alleviated.

But yeah no matter how you slice up the time it's going to take a while to write. When I wrote my screenplay towards the end I became obsessed with it, in fact I almost freaked out and started from scratch like a month before the project deadline but I curbed that.