More or less what I thought, it somewhat depends on if he asks for an upfront deposit, or just states that x% would be charged on the account or CC if the performance is cancelled. Unsure what's culturally more adequate, but at some point it might be necessary being covered from everyone, even good clients who at some point may decide that canceling is a good idea. You need insurance from the facts that seem unexpected, not just from what you know is more likely to go wrong.