Four years ago, builders and contractors flooded into Sacramento's booming market. "They didn't even need to advertise," says Nancy Roberts, a local businesswoman. "But homeowners were getting shoddy work." So Roberts started a local contractor referral service, The Sacramento Trades Guild, for homeowners anxious about hiring carpenters off the street. Today, with the Sacramento market dried up, Roberts has seen the trend shift. Now, she says, contractors hungry for work are eager to get on her list. It isn't that easy. "You can't sign up every contractor in town," says Roberts, who requires contractors to undergo extensive background checks for proper licensing and insurance, past work, and financial stability. "You have to control the quality and make sure members get lots of referrals." Now with more than 100 member