Justin Casse passed on the family training business over 4:30 a.m. wake-ups. Now he owns stakes in about 100 racehorses across six countries

Justin Casse thought he wanted to become a horse trainer like his older brother, but there was just one little problem: the 4:30 a.m. wake-up calls. Fresh out of Florida State University, he was working for his older brother, Mark, caring for animals whose schedules didn’t accommodate weekends or holidays. He wanted a future in the family business, but found himself drawn toward buying and selling horses—a career that would eventually have him scouting thoroughbreds across the world and advising high end clients on investments that could pay off spectacularly or unravel before a horse even reached the starting gate. “Horses don’t know holidays, right? Or weekends,” Casse told Fortune. Now 46, Casse works as a bloodstock agent, helping clients evaluate, buy, and sell thoroughbreds. He also breeds and invests in horses himself, owning stakes in about…