Hardware requirements for building a Debian server that will run as ltsp, vpn, and fileserver

I will be building a server based on Debian that will have several functions in a small office (5-10 users). The primary function will be as a file server, but I would like to set the office up to use only thin clients connected to this single computer. Additionally I have the requirement that users be able to log into their clients remotely over a VPN. I know that a VPN requires two network cards, 1 to the internet and 1 to the LAN. LTSP also uses two network cards, 1 to the internet and 1 to the LAN. For a server to do both do I need to have more than two cards? (i.e. one to the internet and two to the LAN)