He owns that copyright unless he signs it away. Be careful when accepting payments that back of cheque does not contain waiver clauses or 'conditions' etc assigning copyright and rights to reprint extensively to media organisations. they are famous for that, big and small. The owner of copyright usually assigns 'first rights' only when offering for publication. Selling copies individually my gut instinct would be to add a small label at back of photo with with letter c inside circle -- which iindicates copyright -- add words strictly reserved, add his name, date and, if wished, contact number.
Good luck.