How Many User Accounts Are Possible?

Question

I am doing Mac support for a pre-school where they have five Macs, two of which are older iMacs which will only take OS X Panter installs.
We have 37 teachers, about 24-32 of whom will be using them for mail and on a more limited basis, for other things.
They'd like to keep their mail private and I assume other things as well, so my question is: is there a limit to the number of user accounts possible on a Panther machine? I'm guessing we'd eventually like to set up no more than 16 per machine if it's possible to do so without negatively impacting the performance of these iMac 333 computers. They are just barely fast enough to do email, web and word processing etc., so I don't want to slow them down in any way.
. . . and naturally, I won't be setting up fast user switching!
Any input would be appreciated.
JoeL

Answer 1

Thanks to Aldo and Niel for your quick responses!
Just as an experiment, to see how much room a raw account takes up, I used the disk utility to monitor disk space used on the OS disk and looked at:
The space used on the drive with one account (the one I have extant).
After having created a 2nd (non admin) account (but not logged in to it yet).
After logging into that account and creating one textedit (one word) document.
After deleting that account immediately (leaving my one account).
After logging out and back in again to my original account.
The results are as follows:
Disk Space Used (in Bytes):
168,212,189,184 one account
168,213,803,008 two accounts (not logged in)
168,213,823,488 two accounts (logged in/one doc)
168,211,394,560 one account (2nd acct deleted immediately)
168,211,451,904 one account (logged out & back in)
There does seem to be a variability of disk space usage even in the act of logging out and back in with no other activities, but the creation of an account seems to take up very little actual space (as I expected) and I assume, with some variability due to the creation of email accounts & etc, that there would be an acceptable difference between 16 teachers using the same account and creating email and documents and 16 teachers creating 16 accounts and creating email and documents.
These computers don't have the power to run fast user switching without a loss of usability, so I tested the time to switch accounts manually and it's less than booting up, so this is probably the best approach.
Thanks again!
JoeL