create a extension for Joomla 1.7 and integrate with Jomsocial which does what this site do. Allow people to post jobs and accepting jobs. bid on job, invite friends. Check this site for all the basic requirements. Preferably using paypal as payment gateway. With custom fields, and extensive search function based on the custom fields. public and private jobs. Allow activities to show up in jomsocial based on user privacy setting. The admin will have overall control what to show.
PS. if you believe this project budget is too small. We can discuss further. Please place your best bid. I don't plan to own the code either. It only need to be open source so I can edit just in case. I only care about the functionally. You can repackage and resell the extension for all I care.
12 freelancers are bidding on average $1094 for this job
We are a team of computer engineers with an experience of more than 5 years in software development. I am confident our team can provide an appealing quality of work in time.