Freelance book editors provide services to authors before literary agents or publishers come into the picture. The assumption here is that the original manuscript has potential that can be accentuated with a little help.
There are many subjective and commercial aspects you need to consider before you decide to hire a book editor. Some of the subjective elements were covered in an earlier post titled ‘Hiring a freelance editor for proofreading & editing your book’. This one focuses on the commercial perspective.