There are two options. Your son may apply for a student credit card or for a secured credit card.
Student credit cards offer reasonable APRs and low fees. Some of them even have a 0% introductory period for purchases. And your son will be able to build a good credit history if he makes timely payments because these cards report credit performance to major credit bureaus. These cards are good for those who have no credit history.
Secured credit cards were created for those who want to improve or build good credit history and have problems getting approved for a general, unsecured credit card. Secured cards require a security deposit which acts as collateral. So if the payment is late, the bank will use the deposit for payment. Most secured credit cards do not require minimum credit history or credit score.