Frankly if you can not afford to have an attorney advise you...You likely should not adopt.
I'm not sure where you are coming from with this, are you referring to the legal battles that may result from this proposed adoption in the future, or making a general statement that only people with lots of money should adopt? Because if the first, I would agree and if the second, I don't think I necessarily would.
In any event, this proposed adoption sets off all sort of alarms. Where is the child's father? Why is it that the child's mother can't care for her, and what happens when mom decides that she has gotten it together and wants her child back? Where is the child currently living?
In my opinion, this is a situation in which not only do the prospective adoptive parents need an attorney, they should insist that the mother (and probably the father) be represented as well. It would help defend future post-adoption allegations that the mother didn't understand what she was doing, thought it was a temporary guardianship, etc.