Two years ago, no megabank in its right mind would dare originate a jumbo mortgage without asking for at least a 20 percent downpayment – unless the borrower was a special client of the company’s wealth management division. Today, it’s a different story. As refi volumes begin to dwindle, a handful of large banks are loosening their jumbo underwriting standards, allowing for lower downpayment requirements and higher debt-to-income ratios. Wells Fargo has been offering...