Right now we have one laptop and since all of my classes are online after this semester, looking at getting another MBA and putting iMac in spare room to serve as music/video server and spare computer

I would like to back up the laptops but not sure exactly which way would be easiest. Can 2 laptops share one time machine? Can I have both wirelessly back up to an external hard drive connected to the iMac? Would getting OSX server help with this? (Would be a cheap option as I think it's $40?)

Should I buy a time capsule and back up both to it? (Not sure if you can or not)

About same cost for a small external to use for 2nd TM.

I was wrong. It's $19.99

With an external HD, you have to hook it up and run TM, but I am wondering if you can have automated back up using OS X server that way I wouldn't have to worry

I guess iCloud would be the best way

What about 2 partitions on the external so that each is seen as a diff. TM?

You don't have to run it... once you plug it in , have it set to go off at 2:00 a.m.
Then just plug it in at night.

I guess a wireless solution like a Time Capsule would be best, but thats more cash.

You're all really over thinking this. You can use one external hooked up to the iMac to back up all three machines. I'll get back to you on the details when I get home, on the iPhone right now.

Ok good. That's what I was wondering

.....is it Carbonite that you are thinking of?

The one HD will work connected to the iMac. A few things to make note of.

You'll have to make sure that the TM HD is shared in File Sharing Preferences on the iMac, with R/W for everybody.

Connect to the TM HD from the laptops by choosing the iMac in the sidebar and clicking Connect As in the upper right of the Finder window, lock in the sharing password. Remember to log in with the credentials from the iMac, not the laptops.

Double Click on the icon for the TM HD that will appear in the Finder window. That should mount the TM HD on the desktop of the laptop.

Choose the shared networked TM HD that is mounted on the desktop in TM preferences on each laptop.

After you choose the shared TM HD you can eject it from the laptop desktop. The shared disk does not have to be mounted on the desktop of the laptops for this to work, TM will find it on the network.

The iMac will have to be awake to backup, it will not wake on its own when one of the laptops wants to backup.

The first time you run the backup it may ask for login credentials again.

Each laptop will backup to its own sparsebundle on the TM HD, and the iMac will backup to its own backups.backupdb folder on the TM HD, the backups are not mixed together.

You will get much better performance from 802.11n wireless as compared to b or g. If you have a b/g only router you can try it, but if it seems too slow you may consider getting a router that does n speed.

A 2.5" bus powered external USB 3.0 HD is much cheaper than a TimeCapsule. Get a USB 3, they have one cable as compared to the y-cable of older 2.5" USB 2 drives. Even though most machines never needed the y-cable a USB 3 is cleaner as you don't have the extra pigtail hanging off the cable. Amazon has 2.5" 2TB Seagates for $80.

Forget Carbonite. If you want to do offsite backup use CrashPlan. Details here why. It's $60 a year per machine for personal, $120 for business plans. Also CrashPlan is Mac based. The only Windows machines they have are for testing.

I have a local TM backup, and a local SuperDuper for a bootable backup that I run every few days, plus CrashPlan runs 24/7. BTW any offsite backup is a files only backup, not a bare metal recovery backup.