Before a final decree of adoption is passed, the local department and a prospective adoptive parent of an eligible child shall make a written agreement regarding the subsidy. In the case of an eligible child who has special circumstances that existed before the adoption but were not detected until after the adoption, the agreement shall be made promptly after the local department approves the application for a subsidy. A subsidy may commence either at the time of the placement for adoption or at an appropriate time after the passage of the adoption decree. The nature, amount, and duration of the subsidy shall be determined by: the needs of the eligible child because of the eligible child’s special circumstances; and the availability of other resources to meet the eligible child’s needs. The subsidy may be for a limited or a long period of time. The subsidy shall be in an amount that is not more than: the allowable amount for a child under foster family care in this State, or if placement is in another state, the allowable amount for a child under foster family care in that state, whichever is higher; in the case of a medically fragile child living in a treatment foster care home, $2,000 per month; or if the subsidy is for a special service, a reasonable fee for that service. If, under a subsidy agreement, the subsidy does not terminate in the first year after the final decree of adoption is passed, the subsidy is subject to annual reapplication, reevaluation, and reapproval by the local department. A subsidy agreement shall include a notice of the annual reapplication requirement.