In an ideal world, a manuscript will go through at least three rounds of editing: macro (manuscript critique or development editing), sentence (line editing and copy-editing) and proofreading (the final check by team).
But this can all add up.
As an author looking to hire an editor, if your budget is limited you need to decide which service is going to give you the best results.
There are two main arguments people in the book industry make:
The story is more important than correct prose, so spend your money on a manuscript critique or a development edit.
Correct prose is more important than the story, so spend your money on copy-editing and proofreading.
Usefully, these are completely contradictory. Let’s take a close look at each argument and see if we can come to a conclusion that makes sense.