It's even easier than what you describe (note that I don't know any specifics about TS2 though). Use the Traveler mod and change the settings to allow taking friends etc. with you on travel. University uses the travel mechanics, which means you can select any friends of the sim that initiates the university stay with you in one group during the enrollment process, and they will form a temporary household at university. All share the initiating family's inventory. When your one or two weeks are up and you travel home, sims that aren't in your household will go home with you and then proceed further to their own homes from in front of your house by themselves.
You may want to have everyone who goes to university take their aptitude tests before they leave, mostly not because of the money (as an aside, all monetary expenses are paid by the initiating household!), but because you probably want those credits towards the degree. Those "expire" after two days (or was it three?), so you have to switch households around a few times within a short period to achieve that.
I have already done this many times. I haven't stayed at a dorm yet (a couple of times at the frat house though), but that's next, because my next group will be 8 people, though only from two households. This should mean that we have the whole dorm for ourselves - if it works.
