Real estate investment trust New Residential Investment Corp. has been quietly trolling for mortgage servicing assets the past year and snagged a big one this week when it agreed to buy $97 billion in agency rights from Citigroup. Now comes the hard part: incorporating the receivables into an already fast-growing portfolio and convincing regulators at the Federal Housing Finance Agency and Ginnie Mae officials that it has both the management structure and the financial wherewithal to handle so much product. According to a tally from Inside Mortgage Finance, since early December New Residential has acquired...