Curious about the Surrogacy Process!

I originally became interested in becoming a surrogate, because my sister-in-law and her husband are having fertility issues.  I really want to do this for them, but I'm curious about how much the legal costs.  I live in Texas, so does anyone know about them? 

Also, I've had 2 children, and our income is low enough for me to qualify for pregnancy medicaid.  Would I be able to get on pregnancy medicaid if I was carrying someone else's child & we weren't going through an agency?