Build Exchange Website

I am looking for someone to create an exchange website for guest posters. Users can sign up as a "blogger" or a "writer" (Or both); "bloggers" pick the category of their blog and what type of guest posts they are looking for. They buy credits (using paypal api) that allows them to pay per guest post that they accept. Writers have a profile where they can set their areas of speciality, set an "average price" and show samples of their work. Writers bid on projects to earn credits which they can cash out through paypal, or use to get content for their own blog. When a writer writes an article they get to include a linkback to their own site (bloggers can make additional payments to have this excluded, or to have the content ghost written) Bloggers will be able to rate each writer after the completion of the job (this will show on the writers profile). There also needs to be a support system and management system so my customer support team can deal with issues. In your quote please include a price and time frame