I'm talking about a written agreement that's more like an outline of the terms, nothing official
Like for example it could be as simple as this:
You will invest $100000, we will play for 250 hours, I will receive 25% of the first 50000 win, and 15% of any win after that.
Especially if your agreement has any kind of tiers for profit sharing, a verbal agreement can easily become difficult to remember the exact terms of 6 months down the line.
If I need to spell anything out further then that example, I don't want to deal with them, period.