Under Armour

Under Armour started when Kevin Plank sewed moisture-wicking shirts in his grandmother's basement while playing college football, selling them from his car trunk to teammates in 1996. The first prototype—a polyester compression shirt—cost $2.50 to produce and sold for $20, yielding a gross margin of 88%, which is higher than #3 Spanx's initial 70% margin. Plank's targeting of athletes led to $17,000 in sales the first year and $10 million by 2000, a trajectory comparable to the average apparel startup's 10-year path compressed into 4. By 2014, Under Armour reached $3 billion in annual revenue, proving that basement-sewn side hustles can challenge industry giants like Nike.