Pagerank is just Backlinks to your site. Although, looking at your stats, they are pretty good. If i were you, i wouldnt worry about selling any advertisements on the site yet until you have further more traffic. If you still want to sell now then the price differs on where you put the link.
Yeah, $5-10 if that i'm afraid. Also, it's not really a good idea to advertise other sites on your own business, you're just giving people options to click away.