Hi,
I am a native English speaker and full time freelancer.
I do quite a lot of proofreading for large and small businesses, mainly those whose writers are not native speakers. Fortunately, I was born with the ability to spot typos, incorrect punctuation and grammatical errors and inconsistencies from 100 paces.
I also mentor writers and provide a copy editing service.
My average proofreading rate is 2,500 words per hour for foreign writers, so your task of 100,000 words is about 40 hours work @ $29 = $1,160 depending on the quality. If you send me a sample of about 5,000 words then I can provide a tighter estimate.
I have worked with all electronic formats and published books on Amazon for clients.
Happy to chat about your project either on Freelancer or on Skype. I am unable to dedicate a straight 40 hours to the task because of other commitments, so please indicate your preferred timescale.
Thanks and best wishes,
Dan