Harper-Penman began his career with local side Barnstaple Town, playing in their youth team. He attended training sessions in Chivenor with the Plymouth Argyle Development Centre before joining the club's Centre of Excellence in 2008 on a two-year contract. Having progressed to the club's youth team, he signed a two-year professional apprenticeship which began in July 2010. He was promoted to the first team squad in April 2011, along with Jake Baker, after impressing manager Peter Reid while playing for the reserve side. "It's all experience for them being with the first team, and you can't buy that," said Reid. He made his debut on 5 April 2011 in a 2–0 defeat at Leyton Orient, replacing Joe Mason as a second-half substitute. Harper-Penman signed his first professional contract in July 2012.
He joined Southern League Premier Division side Bideford on loan for three months on 4 August. Harper-Penman returned to Argyle at the end of the loan and was released when his contract expired in December. He rejoined Western League Premier Division club Barnstaple Town in January 2013, and scored three goals in his first two appearances. He moved to Frome Town in March until the end of the season, and played in three games. Harper-Penman joined Southern League Premier Division side Truro City in August, having spent time on trial there in pre-season, and made one appearance later that month. He returned to Barnstaple in September and scored in his first game.
