Temporary guardianship with the intent to adopt..?

Firstly, hello~ I am new here, and I apologize if this is not the right area. Now to jump right into it.. A friend of my mom came to me recently and asked me to adopt her grandchild (which is not born yet). The mother has stated she wants absolutely nothing to do with the child (which is her 4th, the other 3 were taken into state custody) and the father does want to know the child, but he does not want to parent it. Both of them asked my mom's friend to find a parent/parents for this child, and so she chose me. However.. at this time, I cannot afford all the legal fees that go along with adopting, and I do not feel comfortable fundraising or asking for help. So basically.. would it work, in this situation, to have the parents sign over temporary guardianship after the baby is born, until I can afford the actual adoption? I do understand the risks, that the parents can take the child back at any time, but that is a risk I am willing to take. I would just rather have the child in my care asap, instead of having to wait until I can afford the legal fees, and then wait longer for the adoption to go through. The mother is 4 months along, so there's still quite a lot of time for one or both of them to change their minds, but I would like to try and prepare as early as possible. I have tried to research temporary guardianship, but I can't seem to find all that much information - just forms to fill out. So.. if there is anything else that anyone can inform me of, that would be super. I guess some info about me may be needed or useful: I am 28 and in Washington state. I guess I am technically single, but I am in a long-distance relationship and we are sort-of engaged (sort-of, because.. 7,000 miles separate us for now), and I'm really not sure how that relationship will play into things. Could/should the actual adoption wait until we are married? He supports me whatever decision I make, though.