Part-time fitness instructors enjoy a lucrative side hustle while staying fit — and helping others stay fit, as well. If you’re interested in becoming a fitness instructor while still managing your ...

Natalie Rose, a U.K.-based certified personal trainer, and barre and Pilates instructor, created the 3-2-8 program. She explains the basics on her website, Bodybybarre, where she also has a 12-week ...