This article explores how people make deals when they can't trust each other to stick to the agreement. The researchers look at different scenarios, like when one person can help the other but might not always do so. They find that in these situations, the best deals involve prices going down as one person gets more help, and the person who needs help feeling better over time. They also study how people share risks when one person controls something important for both. They show that if things are set up right, everyone can end up better off in the long run. Finally, they apply these ideas to the problem of child support, showing how laws can affect how much a parent spends on their child.