The Concord Trailways bus costs about 20 dollars for a one way ticket from the New Hampton Subway sandwich store at Exit 23 to get down to north station in Boston, and it makes the run twice every day and takes about 2 1/2 hours. Boston must have a number of different car rental businesses plus it has the MBTA trolley to get to Logan Airport and a number of car rental spots. Just bring along a couple dollars worth of quarters for the trolley.
To get to the New Hampton subway, you could always hitch hike by holding up a sign that says New Hampton-Exit 23-$9.95!, and you will definitely get a ride or two.....plus let the ride keep the nickel change
. You'll probably get picked up by an 80-something year old driving a big old Lincoln or something like that.