It's a business that has existed for as long as there have been summer vacations and borrowed lawn mowers: A pint-size entrepreneur offers to endure the rage of a summer sun on a neighbor's behalf, pushing a lawn mower across high grass for a small fee. Last week, in Maple Heights, Ohio, that entrepreneur was Reggie Fields, a 12-year-old middle schooler who is the owner and mower-in-chief of Mr. Reggie's Lawn Service. His sister and two cousins also provided manual labor in their neighborhood outside Cleveland, working a rake and a broom to corral clippings. That's what they told Lucille...