When a 7-acre property in Silicon Valley went on the market for $14.85 million, a busload of real-estate agents arrived for a tour. The draw? In addition to the resort-style pool and the putting green, the agents, who specialize in finding upscale properties for Asian buyers, wanted to see the two guesthouses—ideal spaces for aging parents and in-laws.

“I probably did $18 million worth of business with Asians in the last 12 months,” said Arthur Sharif, associate broker at Sotheby’s International Realty in San Francisco who...