VPN server

We want to provide a VPN service on our server so when each user login with his username and password we provide to them, they can surf the internet with our server's IP address. For more info to see what we need please check the following site [login to view URL] The administrator must be able to choose if the user has to use the general server IP address or they can have a private IP for themselves. This service is for countries that have filtered internet and they want to bypass the filter so they can surf the net freely. The service has to support the following protocols: pptp, l2tp, openvpn It must also have accounting ibsng. So users and administrators can login to the control panel. My budget is limited so don't bid high. Let me know if you are going to use a ready-made application or you will do the coding yourself. Only bid if you have done something like this before. If any question, ask before bidding.