I don't think you would need OS X server for that. Have you tried to just establish a VPN connection and then share it? The biggest issue is that you can't share on the same interface. So, you would need to connect to your router over ethernet and then share that VPN over WiFi. I can't test that right now, but you can test it at any time without OS X server.
Oh I know about the Internet sharing functionality in System Preferences, I'm just asking because I might buy OS X Server anyways for school work and having my personal site, email server etc. I've tried to activate it using Bluetooth but for some reason it wouldn't connect to my MacBook Pro, what I'm trying to do now is this: I have a Time Capsule and when I'm at home both my iMac and my MacBook Pro are connected to it, so they are on the same LAN network. Basically what I'm trying to explore with is exporting that VPN connection to SF on my iMac to my MacBook Pro via the VPN on the LAN network on my Time Capsule. So the entire thing would just run on the Wifi interface but instead of sharing my network by inputing the Internet connection in one end and outputting it to another computer on another interfece, I'm trying to see if that connection would work over the LAN network. Thanks anyways.
Even if you had OS X server, you would still need different interfaces. Try it with Ethernet.
Also, you don't need OS X server for either a personal site or an e-mail server. See my User Tips for setting up local servers. You would need to do some additional work relay e-mail, but you would have to do that with OS X Server too.