It is always a good thing to get as much tied down in writing as possible when dealing with unknowns, it helps to keep from having misunderstandings, and helps to protect both parties.
People have a way of "forgetting" the details over time.
If you know them, and trust them, and want to deal on a handshake thats different.
I don't care how many deals you've made or have dreamed you've made, some dickhead always has a way of throwing a kink in it. Yes, hammering out the terms for a deal before making a financial commitment often works well when all parties are honest and above board, but not all parties meet those standards. That's reality.
