The plan is adopted by an employer, and only the income from that employer can be counted. So, if the sole prop adopts a plan, any income received from another employer, whether W-2 or K-1, doesn't count for the sole prop plan (assuming no 414(m), (n), or (o) issues - controlled entities). It's highly unlikely that the 2% ownership will allow him to adopt a plan for that entity, so he has only his sole prop plan and only his sole prop income to take into consideration.