Conversation so far:
When did Eddy Merckx first compete in cycling?
In summer 1961, Eddy Merckx bought his first racing license and competed in his first official race a month after he turned sixteen, coming in sixth place.
When did Eddy Merckx win his first race?
Eddy Merckx rode in twelve more races before winning his first, at Petit-Enghien, on 1 October 1961.
Who was Eddy Merckx's coach initially?
In the winter following his first amateur victory on 1 October 1961, Eddy Merckx trained with former racer Félicien Vervaecke at the local velodrome.

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