hiring a copywriter for a sales page | warrior forum - the ... - how do i determine the ph of skin care products

I'm new to WF ,--
I need someone to write a sales page for my product.
So far, all copywriting I have spoken to would like to charge before or at the time of delivery, but there is no guarantee for the conversion.
But how do I know, after I give the copywriter $3000 (or $5000 or $10000 or whatever ---
They walked away, will the page be converted?
I am not a gambler and I am willing to pay for a valid sales page.
I don't want to pay for pages that don't pay.
How to combine the economic incentives of copywriting with my economic incentives? Does anyone think?