Hi. I am an English professor with 20 years of experience teaching writing at the college level, so my mastery of grammar, style, tone, audience awareness, and documentation styles is expert. I enjoy editing and proofreading, and am extremely meticulous, accurate, and fast.
I have a PhD in English and am a native speaker of US English. I request a high fee because of the high quality of my work and my superb qualifications. You can see my excellent feedback on my profile, along with my skill tests.
What I can do for $500 is: I can easily proofread and lightly edit a manuscript of, say, 350 double-spaced typed pages, in a week. I would use MS Word Track Changes (unless you prefer otherwise), and give overall comments about structure, tone, consistency of style, and so forth. What I mean by "lightly edit" is smooth out awkward wording, correct usage and mechanics, identify comma splices, reorder some sentences for clarity, and other matters along those lines.
It depends what the subject of your book is--if this is a highly technical book requiring specialized knowledge, that will take me longer; or if it is substantially longer than my guess; or if you want substantial editing, e.g. rewriting a chapter. What I suggest is that if you accept my bid, give me the whole manuscript to look at, and then I will edit a small portion--a chapter or portion of a chapter--for a smaller fee, and see if you want me to proceed further.