Maybe:

From the Schedule C Instructions - look at the part I highlighted.

"An activity qualifies as a business if
your primary purpose for engaging in the activity is for income or profit and you are
involved in the activity with continuity and regularity. For example, a sporadic activity, not-for-profit activity, or a hobby does not qualify as a business. To report income
from a nonbusiness activity, see the instructions for Schedule 1 (Form 1040), line 8i."

You and your client need to decide and document whether he meets the above definition of a business.