Since homebuilding is Arizona's main economic engine - and since a home is the biggest investment that most local families will make - you might assume that government officials take great pains to make sure construction here is done right. You'd be wrong. Fact is, thousands of Valley homeowners have been affected by bad soils here. This special report reveals that most of the problems that result from the soils in question are highly preventable, but builders take shortcuts that save them a few grand per house, at the most. They've learned that if they screw up a new home, the only discipline they have to face is, eventually, fixing it. And that's only if the homeowner decides to take on a fight.