Exact rates will vary. Among the factors which can affect rates are: how well written the text already is; how well presented it is; how much work you require beyond simply proofreading the text … and of course how long that text is!
As a rule of thumb, and assuming the text is in a reasonable state, one hour of proofreading work is equivalent to roughly 2,200 words. My current starting rate is £28 per hour.
I accept payment via bank transfer (to a UK account) and PayPal.