The economic fallout from the war with Iran is driving up the cost of buying a home, even as other housing market trends in many parts of the country favor home shoppers this spring. Mortgage rates, which had been trending lower heading into this year, have been rising as the conflict stokes inflation fears. That threatens to put a damper on home sales during what’s traditionally the busiest time of the year for the housing market. At the same time, home shoppers who can afford to buy this spring are likely to benefit from more properties on the market and lower prices than a year ago in many metro areas.