Say a team of canvassers go out for you and get £250 of work. Soon as they give you that work you pay £500 as the x2 as payment.
A lot of trust goes into the canvasser to refund any dropouts and to make sure work is to scratch, however its in the canvassers interest to do a good job so you will hse them again in the future. Soon as they do a bad job or dont replace the dropouts then thats it when the word gets ojt no one will ever use them.