U.S. securities regulators are investigating whether bonds backed by single-family rental homes and sold by Wall Street’s biggest residential landlords used overvalued property assessments. Radian Group Inc.’s Green River Capital unit is one of the market participants that received a request for information from the Securities and Exchange Commission in March about broker price opinions, or BPOs, the company said in a regulatory filinglate Friday. Green River provides BPOs that are used to value real estate in securitizations.