Kalli Ridley had just finished yoga class and was feeling calm when her favorite instructor approached her with a smile and told her she would make a great teacher. “It was like they saw something special in me,” Ms. Ridley said.

But becoming a teacher at the CorePower Yoga studio in Minneapolis, where Ms. Ridley trained, was less straightforward than she anticipated: After paying $1,500 for a 200-hour training program, spread out over eight weeks, she was asked to complete an additional $500 “extensions” training, which was never initially mentioned. For months afterward, Ms. Ridley asked the studio about job opportunities to make money from her training. None ever came. A year later she is still paying off the cost.

At yoga studios around the country, teacher training is a popular way for instructors to supplement income from one-off classes and for students to advance in skill level — to deepen one’s practice, in yogi parlance. It’s not usually promoted as a career path. Rather, teacher training is offered as a kind of advanced workshop.

But CorePower, the country’s largest yoga studio chain, has a distinctly profitable approach : It enlists teachers as salespeople and incentivizes them with bonuses.