Not a new problem, and not one exclusively attributable to illegal immigrants. A person who hires a builder without checking past performance, without confirming insurance, if a fool. The market quickly boots unsavory contractors. Here in Massachusetts, reputable builders have more work than they can handle. Maybe your buddy should move?
My shop tech teacher (trade school...cabinet-building and framing, me) used to say the customer is the boss. Your friend could have adjusted to the demands of the market as required by his clients, but refused. He must be an 'Artiste'.
I hate whining; there's plenty of opportunity that results from every down circumstance in the market. Smart, hard-working folk will get it, and prosper. Whiners demand the gubmint 'do something'.
I know a good harness maker, displaced by the automobile, still looking for work....been 90 years since he had a job.
Note that I put aside the immigrant problem in my nutty last paragraph.