How do you get paid for retyping a book?

Retyping is a service rendered with mutual agreed payment between the customer and the service provider by number of characters, Words, lines or pages typed. It could also be agreed as lump sum payment. The rates for text and scientific subjects like mathematics or chemistry differ. The rates also differ with the urgency, place and with other players who may give a competitive price for retyping. Normally a page of text without editing on A4 size is 1-3 $ per page.