Passage: After his 28-day journey Airoldi was unfortunately not able to compete in the marathon. He went to the royal palace to sign up for the games where he was questioned by the head of the Olympic Committee. He decided that the money received for winning the Milano-Barcellona competition meant that Airoldi was considered a professional athlete and thus not eligible to compete. Telegrams were sent from Italy but nothing worked: Airoldi was not allowed to participate. There was a strong feeling in Italy that the organizers were not allowing a strong competitor to take part in a race that the Greeks wanted to win. Airoldi never accepted the decision and issued a challenge to Spiridon Louis - the winner of the marathon - that was never taken up.

Question: What makes an athlete considered professional?
money received for winning the Milano-Barcellona competition