As residential real estate sales are rising, the luxury home market has declined due to the higher interest rates on jumbo mortgages.  The jumbo rates are as high as 8 percent and a conventional 30-year, fixed rate mortgage is below 5 percent.  Jumbo mortgages are home loans for $417,000 and higher which are difficult to sell on the secondary market.   Underwriting requirements for jumbo loans are strict with no exception to the rules. The banks are being very cautious with these loans, however, a large down payment and a great credit score is favorable for a luxury home loan.