The luxury real estate revival is being fueled, in part, by another resurgence: so-called jumbo mortgages - those loans, typically over $417,000, that are too big to qualify for purchase by federal agencies, namely Fannie Mae and Freddie Mac.

Jumbo loans are returning to the mortgage market after almost disappearing entirely in the wake of the credit crisis of 2008 and the real estate meltdown. Most lenders stopped making new jumbo loans when the private secondary market dried up in the credit crunch.