Some of the nation’s largest home builders might be forced to buy hundreds of acres of desert 10 miles from the Las Vegas Strip at boom-era prices as part of a legal battle with a group of banks led by J.P. Morgan Chase & Co. If a judge rules in favor of the banks over builders such as KB Home and Toll Brothers Inc., it could cast a shadow over a popular but controversial form of off-balance-sheet accounting used when buying land. The strategy is used by builders to insulate themselves from debt and other obligations. The development, called Inspirada, is another housing-crisis casualty in Nevada, one of the hardest-hit U.S. states. Just 635 homes out of the planned 14,500 were sold before financial problems and fighting erupted.