In 1903 John Gray invested $10,500 (approx. $264,000 in today’s money) into a small car company. Fast forward 16 years and Gray’s family sold their share back to the Ford Motor Company for more than $26.25m (around $1.8 billion today). The film star Ashton Kutcher invested a cool £364,000 in a start-up taxi service called Uber several years ago. You’ve probably heard of it. …