For those who would borrow a field from FIRST directly (not AndyMark), they provide exactly what is required and to be considered on their website here:
http://www.usfirst.org/roboticsprogr...considerations
As an off-season, you need to provide your own carpet, tape, tools, etc. Note that the field comes with only the field, and none of the extra cases (no ref items, no safety glasses, etc).
You also need to have appropriate insurance coverage to borrow the field, and more if you borrow the electronics.
While an FTA is required to borrow the electronics, I'd highly advise it no matter what as they have a tremendous wealth of knowledge and experience that extends beyond just operating the field. We've run BattleCry@WPI for 14 years now, and with exception of maybe the first couple years, we've always had an FTA at the event and it's proved very valuable.
If you have any questions about running an off-season, or particularly if any teams in New England are looking for support in running an off-season, just drop us a note and we'll do what we can to help... bc [at] wpi [dot] edu