Hello Im Sourish, I'm a Linux, asterisk, network expert. I can do this for you within few hours.. I would install OpenVPN with a web portal on your server. I would be using standard OpenVPN service and opensource portal script. Its very easy and user friendly to manage the server. You would be easily able to create and download user configuration and start using it. Please let me know and we can talk further on it.
You can try it with me and if you are satisfied then you can pay me. Looking forward to hear from you soon and hope to be a part of this project.
Thanks
Sourish