Need a site with freelancer.com type functionality

Hi, I'm a web designer myself but I've been asked to create a site which is largely database driven and this is an area I know nothing about. What I'm looking for is someone who can create a site around my template ideas and implement database support. The site will be similar to freelancer.com. It is for buyers and resellers of I.T. software/hardware. Users would need to be able to login and submit a request which will then appear on the site for x amount of time in a Latest Requests index, indexes for relevant categories (such as computer monitors) and be searchable. Others can then submit bids on the request. Internal messaging and viewable profiles are also needed. A mock-up design of the homepage can be supplied and used as a guide for the look and feel I want. Many thanks, Bill