Create a VPN with the Raspberry Pi
One possible scenario for wanting a cheap server that you can leave somewhere is if you have recently moved away from home and would like to be able to easily access all of the devices on the network at home, in a secure manner. This will enable you to send files directly to computers, diagnose problems and other useful things. You’ll also be leaving a powered USB hub connected to the Pi, so that you can tell someone to plug in their flash drive, hard drive etc and put files on it for them. This way, they can simply come and collect it later whenever the transfer has finished.
