I have a content website, and the content is very good. I have been doing SEO on my site for four months. I have had a one-way backlink request success rate of almost 20%, and reciprocal link request success rate of almost 65%, which I think is very good. However, I want to spend the little time I get off my university on improving my site, rather than SEO. If I hire someone, or some firm to do SEO on my site, how much should I pay? Will adSense or something similar be able to cover the costs?