N.J. Stat. Ann. § 40A:14-44

In any municipality where there is a volunteer fire company or force, maintained and controlled by the municipality and a part-paid fire department composed of both paid and volunteer firemen, any appointment to such part-paid fire department shall be made from the members of the volunteer fire company or force, who shall have served as active firemen for at least 2 years next preceding such appointment or from among the exempt firemen of the company or force. If no such member or exempt fireman is available for such appointment, any qualified person may be appointed thereto. Said appointees shall not be under 21 or over 40 years of age at the time of the appointment.