The U.S. government has long been a major player in housing finance, mainly by providing the roughly $9 trillion market for agency-backed mortgage bonds with guarantees. - Getty Images President Donald Trump late Thursday revived a longstanding debate within the housing market about what tools the U.S. government should use to make home ownership more affordable. Trump, in a social-media post, said he directed his “representatives” to buy $200 billion in mortgage bonds. “This will drive Mortgage Rates DO ...