It depends. We need to know whether he was unlawfully present without a visa in the U.S. or simply overstayed the I-94 expiration date, among other grounds to start the unlawful presence clock.
It may take ten years from his departure without the ability to prove extreme hardship to a U.S. Citizen or permanent resident spouse or parent. In some situations, a bar on immigration can be permanent as a matter of law or discretion.
The above is general information and does not create an attorney-client relationship.
