Ask What do you do when a client says they will pay more later if the first project goes well?

[Edward22]

I have seen situations where a client promises better pay after the first job, and it sounds like a chance to build a long term relationship. But at the same time, there is no clear guarantee that the promise will be kept. Freelancing income depends on clear agreements, not just words. Taking a lower rate now might lead to regret later if nothing changes. How do you handle such offers without putting yourself at risk of being underpaid?