Software VPN provides the security glue that holds together remote access through the Internet to your Multi-User QuickBooks server. The complete picture appears relatively simple.
Overall, substantial cost savings can come from utilizing multi-user software on a Windows desktop operating system containing a multi-user QuickBooks software installation. Access using Remote Desktop Connection gets secured by VPN software sealing up QuickBooks from any risk from the Internet. Many types of commercial VPN software exist, among which LogMeIn Hamachi seems to be the most widely used.
If you are the least bit technical, gaining familuarity with the “SoftEther VPN Project,” an initiative of the University of Tsukuba in Japan will be a productive use of your time. Their website, at https://www.softether.org/ provides extensive information about software VPN and is a very comprehensive VPN resource.
Deploying “SoftEther VPN” will gain you additional savings over LogMeIn Hamachi. The default deployment, “Remote Access to LAN” described at https://www.softether.org/4-docs/2-howto/1.VPN_for_On-premise/2.Remote_Access_VPN_to_LAN works well as a secure remote network access tool for a small business. The only cost, your time to learn about “SoftEther VPN.”