A question came in this week from a potential coaching client about when to schedule payments on their contracts.
You should get a down payment of some kind, and then a payment about every two weeks. Small jobs should have at least 3 payments. It is better to get smaller payments and more of them. This will improve your cash flow.
Remember, your customers can argue about when some phase of their job is complete or not, but they can't argue about when you start a phase. So schedule your payments at the start of the phase, not the completion.