Being a sponsor

I was asked to sponsor someone from Canada, she has been here over a year and is married to a citizen. They have a 1 year old son. The spouse doesn't make enough to be the sponsor.

I know I am responsible to support her, but say she has some unpaid medical bills before I sponsored her, am I legally obligated to pay them? Or if they will have things turned into collection with both of their names on it, is that my problem as well? Can anyone clear this up for me, I'm somewhat scared to death.

Thanks

Here is some information on being a sponsor. This link also talks about being a "joint sponsor" which sounds like what you are talking about.

http://uscis.gov/graphics/howdoi/affsupp.htm#sponsor

As for the Affidavit of Support: http://uscis.gov/graphics/formsfee/forms/i-864.htm Click on Download. Once you download the form there are a few pages describing what "Sponsor" means. It doesn't sound like you have to pay any previous debts. I think it is for if the individual you sponsor becomes state dependant then the sponsor is responsible for paying back the government.

Thanks so much for taking the time to help me out, I appreciate it.