I think that editing is a murky area for many authors who confuse it with proofing. These are not necessarily the same animal. Here is a bit of my take on the differences:
The proofer is looking for typos, maladjusted lines, margins, grammar, spelling errors, punctuation gaffs, and all the technical aspects of a poem, story, or essay/article.
An editor is more concerned with deeper issues in a manuscript or essay or poem:
Manuscript arc (how do the bits fit together to make a whole?)
Determining if all materials are relevant to theme or arc or if some need to be left out
Order of items in manuscript
What, if any, re-writes are needed for pieces in manuscript
appropriate use of materials
choosing and organizing pieces for an anthology or journal
accepting or rejecting materials submitted to a journal or publication
checking sources/attributions of quoted or cited materials (nonfiction)
formatting of manuscript; making it clean for presentation
publication quality/worthiness (this is a very tricky area, not for the faint of heart!)
These are just some of the many things an editor does to determine manuscript readiness. The relationship between author/poet and editor once was a very personal one, but over time, and due to the sheer volume of materials being published, it has gotten to a different place. Contemporary editors are more technical directors of a manuscript and less of hand-holders, nudgers, and encouragers. I believe in the old way to some extent. Of course there is a difference in "editing" a manuscript for an individual author/poet who is submitting it elsewhere and working on putting together an issue of a journal or magazine. When I work with individuals who want to submit their work "out there" to potential publishers, I prefer the one-on-one approach wherein I work to help the author determine quality of materials to be sent out, to organize materials, and to develop an arc that might jell the manuscript into a cohesive whole. I have spent a long time at this and have a process in place that seems to work well. I want to work WITH an author, not just accept or reject willy-nilly because of my own personal tastes. for my literary journal, Pulse, I often send encouraging notes or suggestions to authors whose work I am rejecting. I think this is a helpful thing, encouraging to the author/poet who does want her/his work to be good.
I also firmly believe we are not the best editors or proofers of our own work. We tend to gloss right over the same errors no matter how many times we comb the manuscript for boo-boos in punctuation, spelling, etc. And we also miss crucial errors in the content and flow of our own work in terms of the narrative, characters, story arc. We need another set of dedicated eyes. This kind of "look" is what editing does for an author.
Having said that, an author needs to be willing to pay actual money for those services. Having your friend do it is fine if that person has editing skills, but ... And if your friend is an editor, pay him or her. If you were a dentist, would you be expected to give free root canals to your friends? You can possibly work out a discount with your editor-friend of course, a kind of "professional courtesy" discount. Go for it if you want to do so. Your friend will still be your friend even if you ask for this.
It used to be that many publishing houses have in-house editors who freelanced. I'm sure that is still happening. You can look for editorial services in most literary marketplace books and listings. Poets and Writers has some ads for these. There are freelance editors out there who offer this kind of service for a variety of fees, some higher than others. It is good to be able to know who is available. Often this comes by word of mouth as well as through conventional sources. Ask around. See who is available to edit OR proof your work once you determine that you want to start sending things out in a serious way. Does every poem need an editor? No. But if you are sending loads of poems out and NONE is getting published, you might look at a writing coach. That is a whole other topic.