some by the completed job.
BS”D
Except that a shadchan’s job should not be considered complete until the couple is married in more than halachic status and name. Yes, some sort of warranty needs to be enforced so that if the couple divorces within X time, or if a hidden issue such as mental illness is found, all fees are refunded. Alternately, fees should be paid into a community escrow and held for a specified amount of time agreed upon by the parties to the shidduch.