I'm a qualified, freelance proofreader, and have been for 23 years. I worked for various local and national newspapers and did private freelance work both here and abroad. I recently did some proofreading for someone who had completed a non-fiction manuscript. I've also enjoyed proofreading - and, on occasion, editing, a few fiction projects. (Oh, I wish I could have proofread all of the Harry Potter manuscripts!)
Last year, I completed my own manuscript on bullying - which has been endorsed by the anti-bullying organisation, Open Your Eyes. (It has had some very good coverage from a few newspapers and radio.) (Sorry, I didn;t mean to boast.)
I haven't worked for a couple of years, so this could, of course, put you off. Understandable - as you'd think I was a bit rusty.