Kent told Inside Edition that Sabastian was 4 years old when he rode a horse for the first time. Since then, he'd been asking his family for a pet horse almost every day.
Kent told CNN Sabastian eventually saved about $2,200.
"I was so proud I almost burst," his mom said. "I was happier than a butcher's dog."
Kent said she was never too worried about the money but wanted her son to learn the value of commitment.
"It was never about the amount of money he saved but actually about his commitment and determination at his age to (achieve) his dream," she said.
Kent told Inside Edition that she kept the whole thing a surprise from Sebastian.
"We had Tom Boy transported overnight and delivered while he as at school," Kent said.
Kent said Sabastian was so happy on the day he met Tom Boy that he stayed on the horse even when he was tired and fell asleep on the horse.
Watch the now-viral video of the big reveal below: