Not too long ago, Brett Karhu’s days fell into a familiar routine. The 22-year-old would wake up, drink the smoothie his wife made for him and arrive at work around 7 a.m., the start of another day as a residential construction manager in McKinney, Texas. Upon his arrival, Karhu would schedule employees for various jobs — pouring a slab or framing a house, for instance — at different sites. ...