I don't know. On one hand, I can hardly imagine jail as a good place to be, on another hand, he needs a serious wake up call.
In our community, about a month ago, four teenagers (17 & 18) broke into a house, and used a knife and a machete to kill a mother and tired to kill her daughter (10 y.o.). The girl miraculously survived. Her dad was on a business trip, and came home to a slaughtered wife and his child in intensive care at a major hospital.
Why did they do it? No reason. They just wanted to rob a house, picked a random one set a bit off to the side, and agreed on killing everyone inside.
The "kids" have been bailed out several times by their parents when they were arrested for this or that "minor" thing (drugs, threatening some kids on the road - following their car too closely, etc.). One can only imagine the heartbreak on the part of every single family involved.
Stealing 1K from a friend does not compare to killing someone, by any means. However, some sort of serious consequence for it is definitely in order, imho. I don't know what I would do, but if I didn't have the power to handle the things on my own (inforce therapy, no car, a have-to job, etc.), I would consider allowing natural consequences to take course. His behaviour is getting progressively worse. SOMETHING has to shake him up before he earns himself a decade in jail for serious fraud.