Conversation so far:
When did Eddy first compete in cycling?
In summer 1961, Merckx bought his first racing license and competed in his first official race a month after he turned sixteen.
When did he win his first race?
at Petit-Enghien, on 1 October 1961.
Who was his coach initially?
In the winter following his first victory, he trained with former racer Felicien Vervaecke at the local velodrome.

Question: When did he start competing professionally?
Self-contained rewrite: When did Eddy Merckx start competing professionally?