Cotton left school in the summer of 1923 and soon started his career as a professional golfer, joining his older brother Leslie as assistant teaching professional at Fulwell Golf Club under Fulwell's professional, George Oke, who had been at Honor Oak since 1921. Within a year Cotton had left and become an assistant at Rye Golf Club near Rye, East Sussex. During his time at Rye, Cotton travelled to Scotland to try to qualify for the 1925 Open Championship. However scores of 85 and 82 left him well outside the qualifying mark of 158. In March 1926, aged 19, he became the professional at Langley Park Golf Club near Beckenham in Kent, replacing Frank Ball who emigrated to America later the same year.