I have an iMac connected by wire to an external (non-Mac) hard drive which is used to store back-up images via Time Machine. I want to buy a second iMac and network the two together. As far as I understand it, this will mean that (subject to permissions) any user can sit at one of the machines and see/use the contents of both hard drives.
How do I now back-up both iMacs to the same hard drive? I can't afford to buy the expensive Time Capsule.
Suggestions will be greatly appreciated.