W hen you're buying a house, especially if it isn't new, you should consider hiring a home inspector to make sure there are no hidden problems with the structure; plumbing, heating and electrical systems, roof, windows or anything else that can affect the price you'd be willing to pay or your decision to buy at all. But it's essential to investigate the inspector carefully before committing to a contract, based on the complaints dissatisfied customers have made online and elsewhere. In a recent undercover investigation, the Washington, D.C.-based non-profit group Consumers' Checkbook found shortcomings among all 12 inspectors it hired to examine a three-bedroom Virginia home. On average, the group said, the inspectors discovered only about half of the 28 problems it had identified in the test house. Among the issues some inspectors missed were unrepaired water damage to a ceiling and walls, an unsafe fireplace and a roof that was in poor condition. It didn...