Income?
Experience?
Back ground check ..For sure
information about their other family members
i would just ask their style of raising a child..Like their method of disipline..
Do they go to church?
Maybe ask them question about their social life..Are they party people that would throw the child off on someone else all the time ..Or home bodies that would actually be loving parents that are there for your baby
maybe ask to see if you could see their home..To make sure its a safe environment to raise a child in..(if thats allowed)
thats about all I can think of right now..Maybe someone else can think of better things for you to ask ..These are the first few things that popped in my head ..Hope I helped:)