Using a Mac Mini as a Backup Server

I go to a smaller college, and I've noticed that hardly any of my friends back up their computers regularly. Most of them don't have more than 100 GB or so on their computer, so backing up would be relatively easy. So I thought that starting some sort of backup service would be a smart business idea.

The whole campus is connected via wifi. My question: what would be the best solution for backing up macs wirelessly? Bear in mind, we do not have access to hard wire internet.

Option 1: Buy an airport extreme, attach it to the college's wireless network, and hook up a couple hitachi 7k3000s in RAID1. For every computer, I would set up a separate partition, and i believe you can password protect each of these with the airport utility, but I am not sure.

Option 2: Buy a used mac mini, attach the same HDD setup as above, and turn file sharing on. Then, like the other option, set up a partition for each computer to back up wirelessly via time machine.

If I chose option 2, how would I be able to secure each of the partitions, so only they (plus the mac mini) would only be accessible to a designated computer? Is OS X server required to do this?

thanks!

 

1. I'm pretty sure torrent protocols or whatever that is called are blocked on the network, although i'm sure they could have previously downloaded stuff.

2. I'm not planning on offering this to anyone i don't know personally.

3. These are BACKUPS. So the worst that can happen if BOTH drives happen to fail simultaneously is that person will lose the backup of their term paper. If their computer hard drive and my two hard drives all fail simultaneously ... i guess God just hates them.

4. I've already set up a time capsule for a friend and connected it to the college's network, and ran it thru the IT department. Had to register the MAC address and everything. How is this any different?