Comment Have you tried TeamViewer? (Score 2) 173
For your main goal of being able to log into your parents' machines, have you tried TeamViewer?
As for setting up VPN, I think you should be able to do it relatively inexpensively with something like a couple of consumer-grade routers running DD-WRT. The one at location B is set up as a VPN client, and the one at location A is set up as a VPN server. You might want to set up address ranges for DHCP at location B such that they're part of the network at location A but not assigned at location A. That way you can avoid needing to do NAT at location B as well as location A.