I recently went on to elance to have someone get me good quiality back links with high pr. We after paying him he did the service but after visiting some of the sites i often wondered how he get my link on there. There was no contact us or submit your site. How does this work? thanks!
Most SEO pro's that offer link building with high PR usually run the sites or are affiliated with the site owners and offer them a certain amount for placing the link on their site. What really sucks though when you buy links not only does this go against google's rules, but also the link you buy usually has a recurring fee. It is recommended rather than buying links to build them yourself.
Some of the link builder own some website. And some will "buy link" through either webmaster forum marketplace or those link selling site
lot of link builders/link building companies have their own network of sites or have partnership or access to these kind of networks. you will not be able to place your link there by yourself but since they have connection with the site admins, they can easily place your links there
in response to people suggesting that link builders have their own network of sites/have a contact list of people who own related sites - i think this makes good business sense personally. it's a full time job looking after numerous sites and i think they have the right to charge what they charge for link building, especially when the results are so good.