People who write and publish stories online typically use a 'beta' or 'beta reader'; someone who performs some of the functions of an editor.
Professionally, I'm not sure how it works, but to get a publisher's interest I believe the general advice is to only send the first one or two chapters, not a full manuscript. Editors are there to help you, but no editor is going to be as good as going over your writing, revising and redrafting as you go. Don't forget that you don't always have to write in order, and revisiting after some time apart from one part of your text will give you a fresh eye and new ideas :)
If you believe everything you read, better not read.