taking custody of someone's child

hey everyone I had an opportunity I never expected come up today. I went to school with this guy and now but weed from him (I'm not currently smoking but my husband is). we have an 8 year old and a 3 month old. today he messaged me asking if I could look up one way flights for him and his son. I asked why to make sure he wasnt trying to run away with his kid. he actually was because of issues with the baby momma. the baby momma doesnt want the boy and hes been having a tough time doing it on his own. the baby was born addicted to drugs and hasn't had an easy or happy life. the mom is still shooting up and smoking meth and the dad wants us to legally adopt his son. I dont know if I'm up for this with the new baby and we were hoping to try again when hes a year old. we have three large dogs and a mini farm on top of the kids. I wouldnt be able to work if I did because I dont make enough to cover two kids getting baby sat. we are already paying $400 a week for our one son. I want to because I love kids and cant stand knowing how this little boy suffers. i have way more than enough love in my heart to give this boy. what would you do?