Son is staying back at college for an unpaid summer project. Who pays for the eight weeks?

He got a place on a summer research project with one of his professors. Good for him. It's unpaid, eight weeks, hostel is closed so he's sharing a room outside campus with a friend. We always assumed summers meant he comes home and costs nothing extra. Now there's rent, mess, travel. Do you cover all of it at this age, split it, or treat it as his call and his budget? He's 20 and has some savings from tutoring juniors.