Hello, I sign the paper work to be my husband’s sponsor, in May 2012, he received his green card. Now I have decided that we need to get a divorce BUT… Since I did sign that sponsor sheet that I will provided medical for him will I still be held accountable to do so if we do get divorce. Or should I just legally separate him so he can maintain his medical through me. I’m going to be a single mother of four and I can’t afford to pay any medical bill for him. Please help… If I have to separate till a certain time then I will do that but if I can divorce him without being held accountable for him that would be better. Thank you

Yes. See Form I-864 (http://www.uscis.gov/files/form/i-864.pdf),
Page 7, under "When Will These Obligations End?"

Note that divorce does not terminate your obligations under this Form I-864.