It’s ironic that people think negotiating a contract with a friend will jeopardize or ruin the friendship. But that is nothing compared to the bitter acrimony, enmity, and outright hatred that results when the deal without a contract sours and goes to court.
The truth is that written contracts often save friendships. Everyone forgets things, and it's often the little details that become fuzzy over time -- and even fuzzier when one or both of the parties' interests or circumstances might have changed. In such cases, a quick review of the written contract often causes one to say, "Yeah, I remember we did agree to that!"
Good contracts are like good fences, protecting friends and neighbors on both sides.