SACRAMENTO — California lawmakers on Wednesday began considering restrictions on unorthodox mortgage-lending practices that have allowed hundreds of thousands of Californians to buy homes they otherwise could not afford.

About half of all new home loans in California are something other than the traditional 30-year fixed loan. They use features such as no money down and variable interest rates, while giving borrowers creative monthly payment options — such as paying only the interest or even less than that.

Such low introductory payments — or teaser rates — are offered in exchange for higher bills that will kick in years later, sometimes tripling or quadrupling monthly payments. Regulators said many of those riskier loans were taken out in 2004 and 2005 and will start resetting to higher rates this year.

"The exposure to these sorts of products, the growth, is unprecedented," Raphael Bostic, an associate professor at the University of Southern California School of Policy, Planning and Development, told a Senate committee. "The regulatory oversight of these types of practices is relatively lax."

Such loans have been offered to home buyers with shaky credit or lower incomes. In other cases, middle-income home buyers turned to them as California housing prices soared in recent years. Such buyers used option-payment adjustable loans and interest-only loans to purchase houses they would have difficulty affording using 30-year fixed mortgages.