I have been asked how much I would charge for cash or a side job and I usually tell them it's more risky to carry cash than a check. Then, I tell them I would have to fire myself for violating company policyc.

They knew I work for myself, too- I don't understand how they could ask me to do something under the table when they should realize that any kind of side job doesn't come with the same protections for the customer and technically, it might void the warranty since, especially if it's an employee, the item(s) don't come from an authorized reseller.