Consider staying at one of the hostels in the area: low cost, very comfortable, and accommodate groups.

http://www.hihostels.com/dba/cmap-US.en.htm

There are two close to the trail:
HI - Eastham: 75 Goody Hallet Drive, Eastham MA 02642
HI - Truro: North Pamet Rd, Truro MA 02666