You're about right, take a look at this:
https://help.ubuntu.com/community/In...n/FromUSBStick
Note though, that the above link really only talks about installing ubuntu on a machine, or running ubuntu live from a pendrive. My experience is that once you create the live ubuntu pendrive, the pendrive can never really be used for anything else!
If you are looking to store updates for ubuntu on your network on any machine, search for information on apt-cache. This is what I do.