Please help. My husband was just told he has a 17 year old child.?

Despite the obvious emotional toll... on both this child not knowing his father and my husband not being able to have a relationship ... do we need to worry about back child support? We can barely raise our own kids!! My husband has not met this child, but we have a picture. We have not had a paternity test done yet... but the picture really looks like my husband. It came from a one nighter when my husband was 17. I am not sure why the mom took so long to find us.The stepdad said they are having probs and now want my husband to step in! I want to move forward and help my husband to have a relationship, but the idea of back child support is making me feel sick and also horrible that i am thinking that, but if we had to pay child support for 17 years, we would have to move and we are already just above poverty level with two kids. We want to do the right thing and establish a relationship now...but this money issue almost makes me feel bitter. Anyone know anything about Indiana law? T