If my son’s father has made little to no effort to contact us in 5 months, how long do I have to wait before I get my husband to adopt him?

As long as there is "some effort", he hasn't hurt the child physically, and he's paying his support obligation, then most courts will not involuntarily terminate the father's parental rights.  Even where a parent is falling behind on child support, if they make some effort to contact the child, then an involuntary termination is not likely to go forward.  If a father does absolutely nothing (no contact, no child support, no indirect support like groceries or diapers), then the courts are more open to involuntary termination if it's been more than a year.  This is for involuntary termination. In order for you husband to adopt your son-- you must first terminate father's rights.  Considering that father has had such minimal contact, he may agree to termination of his parental rights.  You could then file a petition to terminate his rights combined with an adoption and get the ball rolling fairly soon.  As an extra incentive, remind him that the termination would also end his support obligation for the child.  Try to find an family law attorney to help you with either a voluntary or involuntary termination.  If the waiver's are not drafted correctly, it could open the door for the father to come back in later and undo the adoption by your husband.