Put every agreement in writing, especially with friends and family

One of the most common and expensive mistakes in small business is a handshake deal with someone you trust: a friend as co-founder, a relative lending money, a mate doing the website. Nobody means for it to go wrong, but memories differ. When money, time or ownership are involved, those differences become arguments. It doesn't need to be complicated. A one-page email both of you reply "agreed" to, covering who does what, who owns what, what's paid and when, and what happens if someone wants out, can save a friendship as well as a business.