Recent projects I've worked on as a freelance editor illustrate this - some went on to be self - published, others are taking the agent / traditional publication route. (blog.reedsy.com)
Now it is more usual to work remotely via electronic means, and generally I only work on the text unless asked for input on submissions or electronic publication routes. (blog.reedsy.com)
Whatever publication route you take, if you intend the book to sell commercially you have to work your tail off. (accrispin.blogspot.ru)