When I was in business school, I made a lot of great connections (including one with my wife) but only learned two tangible things. Both came from Stanford's famed accounting professor, Jim Van Horne: 1) cash is more important than your mother, and 2) you need an investor with not only deep pockets but also long arms. In other words, you always need liquidity to pay the bills; and you need investors who will be willing to help you when necessary.

When it comes to SaaS and other subscription businesses, however, another rule is nearly as important: Churn is more important than your mother.

Of course, we all know that churn makes it harder to grow your business because you have a "leaky bucket" problem.