@ehBeth,
Actually, I've found Flightcars, which charges very little to rent people's personal cars that are in long term parking (not for me, but nice option for other people), and Zipcars (which I think might be what you're talking about, Beth.) I think I'll get my daughter a Zipcar account for her use - and she'll use it for our visit. She's blocks from Tufts - and on campus, there are three "stables" of Zipcars and a few more in walking distance.
Very happy about this for us now, and her future occasional use. It's a really nice option for students or others who are opting not to have the expense of a car, but want to use one from time to time.
It's like a library for cars...you can use it hourly or daily.
Thanks everybody for the ideas.