My husband wants to adopt my 4 year old son. His Biologial father does nothing for him and never sees him. He said he would sign over his rights but I am afraid that once he finds out that he is signing over his rights so my husband can adopt him he will back out. The biological father has lived in another state since April 2006, since then he has not given any support hasn't seen him since November 2006 and only calls maybe once a month and doesn't want to talk to him he just wants to talk to me. If he backs out what else can I do

Get a lawyer.

He's probably trying to sign away his rights to get out of child support--which doesn't work unless someone is ready to adopt.

If he doesn't want to sign over his rights, get very aggressive about the child support.