I admit, I got lucky when I found my editor. I've mentioned it before in my blogs about the process that I followed to become self-published. There is an amazing website service called Reedsy that I went to find a developmental editor.
Now, there are different editors that you can hire for different services. It depends on your budget. I don't have a large budget, so I hired solely for developmental editing, which is a MUST for self- publishing. There is no way around this when you self-publish. As the writer, there is no way you can't be subjective with your own writing. Hire for this, unless you have a buddy that's willing to do it for you, but they should have a background in it and experience.
Here are editing services you can hire for, in order of how you would do them:
Developmental Editing: Start with developmental editing once you've written, self-edited, and received feedback from beta readers. You don't have to hire someone to do this, but I think it is not wise not to if you are self-publishing. That's my opinion, though. A developmental editor is going to do a fully review of your book, including structure, plot, characters, pacing, etc.
Copy Editing: Copy editing comes after you've done developmental editing, and made changes suggested to improve your manuscript. Remember, just because the developmental editor has suggested a change to your book does not mean you have to take said advice. It is your book. Copy editing will check for grammar, spelling, usage and consistency, correct punctuation and language usage.
Line Editing: Line editing is the third round of editing by a line editor. They suggest changes to make sentences sharp, take out any redundancies and address verb issues. A line editor may also identify awkward sentences and fix structures of sentences and paragraphs.
Proofreading: This is the final editing before publication. This is the confirmation that there are no incorrect spellings, formatting errors, widows and orphans, etc. This is the final polish on your art.
The good thing about Reedsy is you can decide what you want to hire for and you can get up to five quotes from professionals you are looking to hire. Every professional has a resume of their experience and projects, as well as reviews. You can hire for Developmental Editing, Copy Editing (which also includes Line Editing, I believe) and Proofreading. I can't tell you how much these services cost because I have only hired for developmental editing and the cost for my editor may be more or less than for others. There are other variables as well–What genre is it? What is the word count? What is your budget? All you can do is put your information out there and collect some quotes. You do not commit unless you accept an offer and your collaboration begins.
Everything flows through Reedsy–files, messages and payment all go through this website. I've worked with my developmental editor on two books and we can work together outside of Reedsy. But we haven't discussed anything beyond messaging.
There are other ways of finding an editor. Google. I follow several other website resources, such as Writer's Digest, Jane Friedman, and Writer Beware. I talk about Reedsy because I've been through it, and I'm comfortable with it.
Besides Reedsy Marketplace, there is also Reedsy Blog that has some great articles for helping you as well. Remember, before you get to the first editing stage–you'll want to edit your own work!! There's help for this out there! I have my own methods for editing. It's not a pleasant process, but I'm very organized when it gets to the editing phase. I've learned enough to know that by the time it gets to my editor–I don't want her to have to read through a bunch of misspellings and unfinished sentences. So take the time before you hire any professional to do any of the first three to do your own form of editing, even if it isn't subjective. This is a learning process. Do what feels right for you!