Investment banking firms that arrange subordinated debt offerings for mortgage originators are expecting a strong year in 2015, thanks in part to the dismal outlook for initial public offerings. “Sub debt is a good way to grow your business without it being dilutive to your company,” said Bill Dallas, CEO and founder of Skyline Lending, a lender that recently completed a $20 million deal with Ellington Financial, a publicly traded mortgage real estate investment trust. “It allows...