Very good. Now take a look here:
Kentrox - Q2300 Ethernet QoS Access Router
There are two videos to watch. One is Fundamentals of VPN.
Cisco is probably the Gold standard.
You only understood one aspect of VPN which is a a secure link into a "corporate lan" or for that matter a "home lan". Some routers designed for home use have VPN servers built in. Some, however, were blacklisted by
DynDNS -- Dynamic DNS, E-Mail Delivery and Other Services because they didn't adhere to the protocol.
One of the aspects you missed is the ability to extend a LAN, which makes your laptop and your friends laptop and their associated networks to be one small intranet. In this case there is no client-server per se.
What you may have discovered is that this method USUALLY requires static IP addresses. Static IP addresses are usually only available to business class customers.
And thanks for attempting to elaborate so I didn't waste time barking up the wrong tree. It's appreciated.
I don't have experience with this vender, but their products are extremely interesting and worth checking out.
If you are interested initially in a method of securely transferring files between locations, you can implement a secure ftp server at both ends. ssh under the Cygwin environment is in my opinion difficult to set up, but it's free. Look at
Home Page (Bitvise) for other products. That may be all you need to get started. Don't know.
This is the first time I used the "map" method on this site to answer a question and I'm glad it worked out so far.
Remember, I don't know specifically what your planning and what capabilities you need and maybe you don't either that's why I'm throwing out secure FTP as an option.