The family business should be enough cover to get him in. The easiest path will be the F-1.
F1 Student Visa - F1 Visa Immigration
Half the taxi drivers in Washington DC are UDC and regional community college students taking 2 classes per semester just to maintain their immigrant status.
To have a student visa you need to be a full-time student (12 credits undergraduate, 9 credits graduate), show proof that you can pay these courses (international students pay double the rate, so even a community college that s quite a change of money). In addition, you have to have a high school diploma and have passed the TOEFL. It has becoming harder and harder and the US has been losing many students to Canadians Universities due to that and tuition costs.