At a regularly scheduled Monday night practice, more than a dozen eager children methodically rehearse a set of combinations: jab, jab, high kick. As the sweat drips down their faces, there is a sense of accomplishment from the young kickboxers.

Their teacher, Alexis Cardona, walks around the turf and motivates his students, periodically jumping to practice one on one before moving to the next student.

I stayed on my buddy’s couch for months, lived in my car, couldn’t afford rent and e...