If you want to set up a simple VPN remote access for the three computers that are away from the site, it shouldn't cost much at all. The least expensive way to go is a VPN appliance for the main site and VPN client software for each of the three remote computers.
VPN appliances are available from companies like SonicWall, WatchGuard and NetScreen. They should cost no more than $1000 to $2000 for what you need. A benefit of these appliances is that they also provide you a firewall to protect your main site.
To authenticate remote systems to the appliance, you can use shared secrets or simple user name/password approaches. This requires very little set up and training.
The only other thing you will need is a dedicated IP address for your appliance from your ISP. Many inexpensive ISP services provide addresses dynamically via DHCP. This won't work for VPN, since your remote systems won't know where to look to find the appliance if its address changes. So you may have to pay your ISP a little more money for a static/dedicated address.
This was first published in July 2002