I added my almost 22-year-old to a credit card that I don't use with a 3k limit her first year of college. In retrospect, I'm glad I did. She graduates with her undergrad in May, has an over 800 credit score, and a 4% interest rate on the car she bought over the summer. Also, when she went to Australia and Hawaii for work studies, she was able to put expenses on the card and then pay it off with her per-diem without us having to come up with the cash.