Generally, I don't recommend short sales. They provide little or no benefit to the borrower. To the contrary, the borrower, who in this case is your wife, could be faced with forgiveness of indebtedness income. That is the difference between what she owes on the mortgage and what they receive from the sale. The IRS considers that income and the mortgage company will likely issue a 1099c requiring that she report that as income.
However, if she simply allows the house to go to foreclosure, there should be no forgiveness because the debt was not forgiven. It is then unlikely the mortgage company would pursue any deficiency as they generally settle for whatever they get from the property.
If you are determined to proceed with a short sale, your income information does not make you liable. Rather, it is merely a way of determining theoretically whether the mortgage company could have pursued your wife. It is an academic exercise.
Answered on Feb 15th, 2013 at 5:50 PM