Nationstar Mortgage this week priced $300 million of asset-backed notes in what the company called “the first ever” securitization of collateral backed by agency servicing advances, a sign that nonbanks are beginning to see more liquidity for mortgage servicing rights. The yield on the Nationstar paper is an attractive 1.46 percent. The term is three years. And in another development in the same market, Home Loan Servicing Solutions, which is affiliated with Ocwen Financial, has signaled...