From your comment, you may be in search of a manuscript critique, where you pay a professional to essentially conduct a beta read with the added benefit of their experience and knowledge about the craft. Then they’ll give you a few pages’ worth of considerations. When I don’t have the time for such critiques (and I only critique nonfiction), I refer my clients to andilit.com.
Working with a professional is always the best choice, so if possible, then save up to work with an editor. But of course, some writers can't afford this, in which case there are some other options. You can barter with other writers in the same genre, editing each other's work, or providing other services you might be more skilled at e.g. Marketing tasks.
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.
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.