Almost every writer I've worked with has been strapped for cash and can pay for nothing more than proofreading. For this reason, I've always then done copy editing along with proofreading, and sometimes I've done some content editing as well on the same pass through the material--because I really do want to help authors publish readable, enjoyable work. What annoys me in this process is a writer who EXPECTS this kind of service and EXPECTS to get it for free.