Hi, Robert E.
If you use Upwork correctly, it is a lot more difficult for a client to try to get free work from you.
Don't work without Upwork telling you there is a contract with the client.
If the contract is for a fixed price with milestones, don't start work on a milestone until Upwork tells you that milestone is fully funded and the client has released escrow payments to you for all previous milestones. Only submit finished work to the client using the "Submit" button on the contract's Upwork page.
If the contract is for an hourly arrangement, do not use manual hours to record your work time. Install Upwork's TimeTracker app on your computer and always invoke it when you start work and stop tracking time when your work session is over. Include for each work session a clear and concise memo for what you are doing during this session.
The Upwork Web site includes clear instructions on how all of the above works for you.
If you and your client are using Upwork properly, you will be told by Upwork that money is available to you a) five days after each milestone is submitted by you and approved by the client (who has 14 days before escrow payment is automatically released), or b) each week with some delay after the Upwork work week ends and your tracked work hours are added up as of midnight Greenwich Meantime (UTC).