I have reluctantly got Quickbooks 2006 and it is slow on my machine, so could not imagine it over a network.

Quickbooks local helpdesk is useless - they dont get back with solutions and generally do not have any answers readily at hand

Then considering that Quickbooks told MS where to put Vista and their certification programme, and do not seem to have been very inovative in upgrading their software, (2006 looks and feels the same as version 3 that I bought many many years ago), I cannot see that they even know what VPN stands for or how it works.

My recommendation is that if one can avoid Quickbooks then do so.