I've done four covers through Ebook Launch for two different series, and they've knocked it out of the park every time. In one case they were creating brand new covers based on a high-concept mashup idea. In another, they were following in the footsteps of a different designer, who'd already established the look for an existing series. Both times -- whether coming up with something totally new or sticking to an established style -- they did fantastic work. I love my Ebook Launch covers!
OUR EDITORS are confident, calculated, experienced and ruthless. We tend to look for people with at least an MA in Literature and 2 years of full-time book editing experience, but will also give editors a chance if they’ve edited at least 10 books and can provide references from happy clients; or if they’re successful authors themselves who have published several books.
There’s a big difference between editors who point out your weaknesses and come up with solutions, versus those who give general advice that doesn’t go anywhere. One author who kept getting generic feedback from editors that amounted to, “It’s good, keep writing,” ended up with a 215,000-word tome. The weary man finally found an editor who was able to show him how to cut the manuscript in half and tighten the plot.

Start with a google search and see what comes up. Click on a handful of options and see if you can find an editor who is specialized or who has edited books similar to your own. An easy way to do this is to open just a few of your favorites in tabs and check out each editors’ website and about me section. Take a look at their testimonials. See if any stand out to you.
A site where you can hire editors on a freelance basis. Has a range of prices so there is something to suit most budgets. Be sure to take the usual caution when working with a freelancer. Check out their reputation carefully first and communicate carefully with them in order to determine a schedule, payment expectations, methods of communication etc.
An edit requires a substantial investment, many times greater than the cost of a book. Editors who spent years as assistants, learning the craft of editing and acquiring the knowledge of how to guide authors, are a safer choice. Their track record speaks for itself; editors at this level have bestsellers and award winners in both the traditional and the self-publishing space.
Regarding your last question, I know of no editor who gives a money-back guarantee for occasional errors that happen to slip through or for a different opinion by a later editor. I’m afraid such things are just the nature of the publishing beast. But by having a shorter portion edited first, you will get a decent feel for whether someone is the right editor for you, and will be able to be confident in his or her work on your entire book.
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