Any shadchan who accepts payment before a marriage is contracted is going against halacha. Please don’t call that person a shadchan.
AZ, maybe you can start a dating agency with these conditions. In that case, a dating agency can take a fee up front to set up dates according to the personalities, needs and compatibility of the parties (like the goyim do). Under these conditions, whatever arrangements are made beforehand that everyone agrees to are appropriate. But then these are not shadchanim, these would be dating agencies and the workers are entitled to get paid for their work, as are anyone employed by them.