Paying everything at the end is risky for the worker. Paying everything at the start is risky for the client.
A deposit and milestone plan shares the risk. For example, pay a part at the start, a part after the first draft, and the rest after delivery. Link each payment to a clear result, and say work can pause if a payment is late.
Tip: write each milestone as something you can see and check.
General information only, not legal advice.