LOS ANGELES - Kristin Zimmerman went looking for a new apartment recently after someone broke into her unit in a converted Victorian house in the Pacific Heights neighborhood of San Francisco. She found a roomy, two-bedroom, two-bath dwelling on the edge of upscale Russian Hill, where the previous tenant had been paying $2,600 a month - more than the $1,959 a month she and her roommate were spending but still within their limit. The landlord, however, wanted $3,000 a month and wouldn't budge. "The woman was just unrelenting," said Zimmerman, 26, a cancer researcher. Apartment rents and demand are soaring...