You should not work on the project unless there is a formal offer from Cline and you've accepted it.
After the contract is in place:
If the project is hourly, please make sure client's payment method is verified. You can share the link while working.
If it is a fixed fee contract, split it into multiple milestones, at least two. And before starting to work ensure the milestone is funded and activated. Here is an example: If the total number of slides needed by clinet are 10 for $20 dollar per slide. And if the client funds $100 dollar you should work only on 5 slides and you can share the link, because only after reviewing the work the client will release the payment.