Business network VPN

Hi peeps,

To cut to the chase: I'm attempting to run a business entirely on Linux (Ubuntu and Linux Mint) with open source software (some moral philosophy I seem to developed randomly). So far it's all good; all invoicing, web design (and management, and the backend itself), accounts, etc. are done on Linux using open source software. Problem is, we've grown a little quicker than anticipated and I don't want to employ any IT company (the last five I had round kept telling me that I MUST use Windows..didn't go down well). I need a VPN or similar so that everyone can log in and access everything, their own login, etc. Anyone know any good guides for anyone that's only ever dealt with LAN and normal desktop Linux stuff?

Cheers :)

Elliot