Carpentry in a tiny hamlet of less than 100 families in an isolated valley was hardly a lucrative job. Wood was scarce in the area, and St. Joseph would have had to pay a good amount for the little wood available just to make it into something. He would have been in no position to mark up his costs a lot to turn a handsome profit. Besides, carpentry was somewhat looked-down upon as a profession: necessary, sure, but kind of like “leftovers” as far as honorable work would go. St. Joseph would have been able to provide in his day, at best, what we would today call a lower-middle-class lifestyle.
The Gospel’s don’t actually call Joseph a carpenter. That’s just a translation, and a rather poor one at that.
St. Joseph was a “tekton”, which means an artisan in wood, stone, and iron. He was a builder.