An "A" grade customer is one who ticks all the boxes. Good access, easy windows, nice people, good price, right location, good parking etc.
A bungalow with a side gate thats never locked, has parking for my van, and pays £15 would be a grade A job.
They are not that easy to find but they are around. Once you get one you can drop one of the grade C jobs thats been bugging you.