When parents are found and approved for adoption of a child certified as eligible for subsidy, and before the final decree of adoption is issued, there must be a written agreement between the State Department of Human Resources and the adopting family as to the terms and conditions of the subsidy. Upon determination of eligibility, adoption subsidies in individual cases may commence at any time after the adoption placement or at the appropriate time after the adoption decree, and will vary with the needs of the child and as negotiated with the adoptive parent or parents, and according to, as well as the availability of, other resources to meet the child's needs. The subsidy may be for special services only, or for money payments, payment deferred, and either for a limited period, or for a long term, or for any combination of the foregoing. The amount of the time-limited or long-term subsidy may in no case exceed that which would be allowable for such child if the child had remained in foster care, or, in the case of special service, the reasonable fee for the service rendered. If the adoptive parent or parents move to another state of residence with the child, the adoption subsidy payment shall continue if the child's needs remain the same and the child was a resident of Alabama when eligibility for subsidy was certified. Payments shall be made to the legal parent with physical custody of the child except for school or other parent authorized placements unless otherwise ordered by a court or by signed agreement by the parent or parents and the department. No payment may be made to a parent or parents if the child is not a citizen or permanent legal resident of the United States unless the child was adopted outside the United States and brought into this country for the purpose of adoption and the adoption failed and the child was placed into foster care.