if you were selling a one time service, let's say one tree, or a mulch job, or whatever, something that would only be done one time. do you demand payment, in full, BEFORE you do the job? or, as a businessman and a good one, who would like to deliver the job, see a satisfied customer, then have the bill paid, do u do the job, and get paid upon completion and satisfaction? simply put, before, or after?