My 15 year-old son made around $400 from Youtube. He wasn't provided with any 1099-MISC. How should I file that? Is it treated as a self-employed business?

My 15 year-old son made around $400 from Youtube. He wasn't provided with any 1099-MISC. How should I file that? Is it treated as a self-employed business? He(actually I) pays $25 fee per month for a video editing software. Is that an expense?