Inter-Family Adoption

I am a 23 year old mother of two. My sister is 21 and is pregnant and just got out of the relationship with the child's father. My sister would like to put the baby up for adoption and the father is fine with that. However, my family is not real keen on that idea. My husband and I had planned on having a 3rd child, but due to some health, fertility affecting issues we're not sure that will happen. I would love to bring her child into my home and raise him/her as my own, and also that way my sister could get to see him grow up. I realize there are families who need a child much worse than my husband and I, but we would like to keep this baby within the family. Does anyone have any feedback? Does anyone know where I can get some free advice on how to go about doing this? Any help would be greatly appreciated. Angel Blue