Some industry analysts suggest that originations of purchase mortgages have been held back by potential borrowers’ debt-to-income ratios, which have increased along with rises in home prices. However, originations of purchase mortgages have increased in the past year as home prices have risen and it’s more than DTI ratios shutting certain borrowers out of the purchase market. Even though interest rates on mortgages remain at relatively low levels, housing affordability has been an increasing concern due to trends in home prices. Borrowers in parts of California, as well as Denver, Miami and Portland, could have difficulty qualifying for a purchase mortgage, according to a recent analysis by Zillow. Based on income, mortgage and home-value data for the fourth quarter of 2013, Zillow found...