In other states they can sell the house and bill you for the remainder of the mortgage, and you don't even have a place to live out of it.
—In California, walk away and the bank has no further recourse. —
This. You’re gonna have to check your state’s laws. I do have one acquaintence that has not made a mortgage payment in two years and still lives there, the whole time trying to work something out with the bank to no avail.
And at the rate people are walking away, any bank that DOES try to sue you (assuming they can in your friend’s state) is gonna have to wait in line for a court slot, maybe several decades. One car speeding is a ticket magnet. A car speeding in a pack of a thousand speeding cars, less so.
The situation may be different for purchase-money and refinance deeds of trust. Consult an attorney; I'm not an attorney.