NEGOTITATOR

Payment of parts (a deposit) or all of the charge for services yet to be performed; but will the service be performed afterwards?

Avoid advance payments to people you do not know. If they are short of cash, they are unreliable. If, plausibly, they need money for materials, buy them yourself and deliver them to your premises not theirs.

If a reputable business wants an advance payment (get a signed and dated receipt), require a discount on the price at least equivalent to the interest you lose while they have money. Banks do not lend money for nothing, so why should you?