As a co-signer, how will my credit be affected if we walk away from property in foreclosure?

I co-signed for my son for a condo five years ago. He and his partner run their own business. With the ecomony the way it is, he is not getting paid and therefore unable to pay his debts. He has now been notiifed his property will be in foreclosure. The bank has given him options. One option is to just let it go. I know my credit is affected and I am a senior ready to retire soon. I considered taking my own money out to make him current, but I don't want it to just go into a "black hole". I want to know what the ramificaitons of that decision would be for me and for him if he simply lets the property go. I still have a mortgage on my own home, car payment and before this always had excellent credit. What can I do to protect myself. I need an answer quickly please. THANK YOU.