I don't use contracts for residential work, but all regular residentials expect and receive service from me when I determine the time is right. I'll throw in one-time mows for the next door neighbors and such as time permits, but I don't let it cut into my service to the regulars. If a one-timer's yard is overgrown I might double mow, but no extensive cleanups and no bagging. I let them know the hay will lay there or pass on it. Also I don't get into bigger jobs with people who don't also receive regular service.