I'm not a CPA, but have done a bit of research on this topic. The bank will send your client a 1099, but this taxable income is tax exempt if the loan balance is less that $2 mil and it's their primary residence. Also, the loan must have been used to buy, build, or improve a primary residence.
Possibilities for tax exemption from forgiven debt:
*Qualified Principal Residence
*Bankruptcy
*Insolvency (total debts outweigh current market value of assets)
Have your client talk to a CPA. I frequently reference the IRS publication 4681: http://www.irs.gov/pub/irs-pdf/p4681.pdf
Have your client review this document and come to their own conclusion or even better, consult with a CPA. Educate yourself a bit on insolvency as well - it saves the majority of people from pay taxes on the forgiven debt, regardless of the details of the loan(s).