Just to give you an idea…I am an excellent editor (so say fellow writers) and I went through book 3 maybe…twenty times? Something like that.
Then I read the whole book, one chapter per week (!), to my writers group (that’s 8 writers on average) and they all edited and proofed at their best.
THEN I read the audiobook and by reading out loud and re-listening I found still a bunch of the litter suckers (typos, that is).
Finally, I sent my final draft to my proofer. This is what came back:

So, how do you find a good proofer?
You have to connect with other writers, they are your most valuable resource. You could get a recommendation from someone in your writers group or, if you are broke, you could offer to proof somebody else’s work in return for proofing yours. Of course, you have to know the person and they have to value your work.
I found that finding a proofer was hard with my first book, but since I’m working on a series several readers (professionals!!) volunteered to proof for free to read the next installment in the series first (and for free) ;)
Good luck ^_^
GBA
Register for my monthly newsletter with links to all my posts at www.gaiabamman.com The free writers’ guide is coming!