Looking for a place near Boston to store a car long term...

My mom owns a summer cottage in New Hampshire. It’s been in the family for about 40 years, and is absolutely paradise. As far as vacations go, it’s great except for one thing–she has to rent a car when she goes there, because she lives in Arizona. (When I go, I drive up, because it’s only about an 11 hour drive from here).

So this year she is buying a car. This will end up being much cheaper in the long run than renting a car for a couple of months every summer.

The problem is that she doesn’t have anywhere to put the car during the year. She will be using the car June - September every summer, and needs to park it somewhere safe the rest of the time. She wants it as near to Logan airport as possible, as that is where she flies in and out of.

Help?