A legal question

legal question. A situation has come up where we may be adopting two children from the same birthmother. We had not planned to adopt this soon and have not gone through the homestudy and such (but this should not be a problem, we should qualify without a hitch) The 1st baby is 6 months old and Bmom just found out she was pregnant. She has decided she wants us to adopt the 2nd one for sure and is still trying to decide to keep 1st child or place him with us also. (this is a friend of the family) now to my question. If we go through with these adoptions what is the lenght of right or recision? I have heard that in AZ that a bparent can have up to a year to change thier minds about an adoption? I have also seen that it's only 24 hours to 8 days if it's a newborn? HELP... I don't think I could raise these kids as my own only to have them taken back at the end of a year.