Sara Blakely was 29 when she invested her entire life savings, $5,000, trying to come up with something flattering to wear under her white slacks. Six months later, she found her new line of shaping underwear, Spanx, named one of Oprah Winfrey's Favorite Things. Since then, Blakely has taken Spanx from a one-product wonder sold out of her Atlanta apartment to a billion-dollar powerhouse with just under $250 million in annual revenues and net profit margins estimated at 20%. She owns 100% of the private company, has never advertised and never taken outside investment. Blakely turned 41 in February, making her the youngest female self-made billionaire in the world.
