Well-sinkers were quite important in some ways - before the days when you could call the plumber, then if you wanted water, you often had to hire a well-sinker (who might also be a well-finder, in the sense that he often decided where the best place would be, to sink a well.
So it's is possible that some well-sinkers (own business !) could be quite well off; for others it may have just been "a job".
Bob