Today one of my Twitter pals asked if it's worthwhile for an unpublished writer to have her manuscript professionally edited before sending it to a literary agent. At the risk of offending those who make money editing manuscripts for unpublished writers, I must say that paying a "book doctor" to edit a manuscript in the hope that she will transform it into a salable novel is a colossal waste of both money and time.
Self-editing is a huge part of writing well. A writer who has not yet learned how to ruthlessly edit her own work simply isn't ready for publication. Even major tweaking by a paid professional won't turn the lackluster manuscript of such a writer into anything that would interest an agent or a publishing house.
Publishers are used to looking past grammatical and punctuation errors and even awkward scenes dropped here and there. They know all that stuff can be cleaned up because they do it every day. They're always impressed by a "clean" manuscript, but what they're really looking for is a gripping story told by a talented and skillful writer. That being the case, paying a book doctor to make your story more tempting to agents and publishers makes about as much sense as painting a pig's toenails so it will fetch a higher price at the livestock auction.
A published writer is someone who has learned how to edit her own work. She knows how to tell a good story clearly and concisely. She puts words together in such a way that her sentences sing, her paragraphs dance, and her scenes and chapters begin and end gracefully. Some of that ability came from raw talent; the rest she developed through hard work and by paying close attention to the technique of published authors she admires.
Have you ever eaten at a restaurant where the paint was peeling off the walls and the table was sticky but the food was fabulous? If so, you probably went back again and again for the great food. Contrast that with the experience of dining in a scrupulously clean establishment with cloth napkins and sparkling glasses--and ordinary, unimaginative food. Do you go back to those places? Not if you can help it, you don't.
Publishers know how to take a great story told in an engaging way and turn it into a good book. They're not afraid to buy manuscripts that are a little bit awkward, a little bit messy--as long as those manuscripts sing and dance and fascinate.
The bottom line? Depending on your current level of writing skill and how teachable you are, paying a reputable freelance editor might help you learn some valuable lessons about grammar, word usage, and basic story structure. What it will not do is take a story that's not quite ready for publication and turn it into something wonderful.
You will have to do that all by yourself.