Dozens of designers, landscape architects and contractors transformed the 11,000-square-foot Tudor home's rooms into showpieces, all at little cost to the seller. The 1980s kitchen—likely to turn off potential buyers—was gutted and rebuilt with the sleek cabinets, intricate tiling and Sub-Zero refrigerator that shoppers were likely to look for. A modern limestone soaking tub replaced a dated, wood-paneled Jacuzzi tub, and tired landscaping was refreshed, said Ms. Pomphrey, an agent with Coldwell Banker Previews International in Rumson, N.J. "Now, you could just move right in," she said. Decorator show homes are a beloved tradition in many U.S. cities. The show-home season typically kicks off when the warm weather sets in, and the homes stay open to the public for three or four weeks. Visitors pay an admission fee of between $25 and $60 to tour the homes; the money is usually earmarked for a charity. After paying for things like insurance and electricity, most show homes raise between $100,000 and $200,000, organizers say. But charities aren't the only beneficiaries. Show homes thrive on sponsors and donations: Few involved are paid for their work, though almost everyone aims to benefit. Designers put their best work forward to attract new clients. Furniture and equipment suppliers receive free publicity. And the homeowner is often looking for help improving—and ultimately selling—the home.