The Unexpected
Like many aspiring entrepreneurs, Rich Devos & Jay Van Andel started a number of  businesses before finding their niche as the founders of Amway. Their first venture was in the aviation industry. The World War II veterans opened a flying school in Michigan, but after hiring instructors and signing up customers, they discovered there was a slight problem: the newly constructed airport had no runway, unless you counted the large mud puddles where the landing strip was supposed to be located. And contractors hadn't yet built their small office which was to be located nearby.

Lesson: Suppliers or service providers may not meet expected deadlines, so always have a backup plan.

Reference
Conn. C.P. (1978). The Possible Dream. P. 6.