I made some side money as a student by creating and maintaining a DB app for a local dealer of a particular brand of chemical products. The owner had a simple r

I made some side money as a student by creating and maintaining a DB app for a local dealer of a particular brand of chemical products. The owner had a simple rule - customers pay upfront unless the sum was large enough for him to sue for. He had a de facto local monopoly so he could afford to enforce this. Obviously it didn't apply to trusted customers.