You probably already know what sorts of work editors do. Here are some definitions, if not.
* A copy editor deals with issues of grammar, spelling, styling (for instance, does the use of capitalization, of quote marks vs. italics, of hyphenation, etc. follow the styles of the U. of Chicago Manual of Style and of the publishing house’s own style guide?), and–too often—of pre-preparing copy for the typographers.
* A line editor deals with larger issues of sentence construction, avoiding repetition, etc.
* A content editor, or substantive editor, deals with larger issues
of organization, both within and among the book’s chapters.
* A developmental editor deals with even larger issues of the book’s organization, and may suggest adding characters, possible changes in structure or point of view (and even in plot elements), etc.

These functions tend to overlap; for instance, most publishers will combine developmental, content, and some line editing into one job description, termed that of “the editor” or, perhaps, “the substantive editor”; nearly all publishers combine line editing and copy editing into one position, term it “copy editor,” and
pay at the lowest scale they can get away with, whereas some publishers, otoh, combine copy editing with some proofreading and typographic copy preparation and pay at the very lowest scale that they can barely get away with.

With individual clients, editors often combine most of the “higher level” editing functions into one, termed “editing”; a general critique of a manuscript, with few or no edits/comments noted on specific lines or paragraphs, and with a several-page letter developing major points about changes preferable for the manuscript, is called a manuscript critique.

Rates range from $20/hour for basic copyediting from low-paying presses to $90/hour for a manuscript critique with some example edits by a known writer or highly regarded editing professional.
Is this set of defiinitions of use to you? Please do let me know. Remember, this is a new blog, and your input can definitely affect these discussions.