…Treasury officials also are focused on the government’s role in making mortgages affordable for lower-income borrowers, the people said. Michael A. Stegman, who joined Treasury this year as a counselor on housing finance policy, once headed a research project on affordable homeownership at the University of North Carolina that made the case that loans to low-income borrowers performed well as long as the terms were similar to those given to borrowers qualifying for prime rates. “We’ve got fairly good evidence here that carefully structured financing for lower-income households to buy a home can be very successful,” said Janneke Ratcliffe, who now directs the Center for Community Capital, which Stegman founded.