Access computer over Internet
I understand his requirement, but as have also mentioned that, he needs permission from organization to host VPN server on his machine, which mostly he will not get (generally) only limited persons get company VPN access.
And what I said is possible, may be you didn't get it, and I said that because I am doing that sucessfully.
Let me clear what I do:
What I do is, I have my VPN server on my home laptop, while going from office, I start connecting to that home VPN server, and in configuration I have kept it to infinite tries, and use dynamic host name service to avoid purchase static IP.
So when I go home and start my VPN server, the office machines gets connected to my VPN server (as it keep on trying to connect my home machine), and then I can access everything of my machine.
So from home I can access my workstation machine, or take remote of that.
I am using OpenVPN Server and Client for this.
For any kind of access to his workstation machine requires port to be open in his office network, so the only way out is to send request from inside network to outside. Because by-default no ports are open from outside to inside network, but from inside few ports are open to outside network (public) like HTTP (80), HTTPS (443) or FTP may be. So his request can go out on these port numbers and then tunnel will be formed within that port number between which whole data is travel. But if he send any request from outside to his workstation machine, that packet will be dropped on his company's router, because NAT is being used and firewall's are there.