I can write you a purchase order today that will commit me to paying you a 10% commission when I sell 10,000,000 widgets at $20.00 each WHEN I GET PAID. If I don’t sell any widgets you get nothing or better yet if I sell some widgets and don’t get paid for my widgets you get nothing. What if nobody wants my widgets or my widgets are overpriced or my widgets are obsolete? I owe you nothing. It’s not a contract, it’s a piece of toilet paper.