I like prompt payment, they don't pay for custom orders... I don't make it. At least a deposit, just in case I need supplies. The balance due when the item is finished and custom listing is live. In my policies, If payment for your purchase has not been made within 72 hours (3 days) of purchase, the transaction will be cancelled.
I don't do custom orders anymore, but when I did, I had that in my policies, about the deposit.