I second benhila's comment. "In construction" is an awfully broad description -- if you could give a bit more information about his experience and skills (and where you plan to live), you might get a useful approximation of the earnings he might expect, and of the lifestyle you might be able to afford.
There are an awful lot of young tradesmen on the projects that I'm assigned to that have an enviable collection of man-toys (boats, quads, motorcycles, and the like), and not too many seem to be still living with their parents, so they're not starving.