I like the idea, however it appears as if the buyer has to wait until the seller has done the work before sending them payment. How much confidence could the s

I like the idea, however it appears as if the buyer has to wait until the seller has done the work before sending them payment. How much confidence could the seller (i.e. the person doing the proof) have about the buyers ability to pay before they embark on completing the work? A much better approach would be the buyer puts up the problem they want a proof for and then pays an escrow service, that way you can have more confidence that payment will be completed.