You also said it’s not fair for self-publishing authors to apply those standards to editors when they don’t work with publishers themselves. It’s one thing for authors to have the right to publish their work and make it available for readers to judge its merits, and quite another for someone to ask those authors to invest in them for their expertise.
We’ve set up a unique “first chapter critique” service which includes up to 5,000 words (which should actually include 2~3 chapters… or a prologue, preface or intro). This will be an deconstructive developmental edit, pointing out exactly where your weaknesses lie and what you can do to make them better, but will not include a full edit or proofread. We will, however, edit your blurb, bio or query, as long as they fit within the 5K word limit.
Next, I check their work history to see what kind of projects they have been working on. For example, if I’m hiring an editor and I see that 8 out of their last 10 projects had nothing to do with editing, I will probably pass because it means they either don’t enjoy editing work or they aren’t able to find enough of it on Upwork, which should not be a problem for a highly skilled editor.
Work in house first. That’s the best way to learn all you can about editing and proofreading and make good connections. I have met several people I’ve worked with from hanging out in Twitter and responding to tweets asking for an editor or proofreader, but I have had the most success from business connections I made while working in in house. Other things – a web site, professional associations such as the SFEP and the EFA (though I can’t say much more on these as I am not a member of either yet!), social media.
Obviously there is a big difference. I actually started with screenplays (with some mild success) partly due to hearing that as long as you have a good story, the grammatical errors won’t be a big deal. Well, that was not true. Maybe if a producer liked the story or I was already established but every contest I entered always came back with feedback about the grammatical errors. Even if I won or placed as a finalist, I always received critique on that. Very little is spelling error, it was more about structure, etc.