which qualifications are required for the post?
They should be least 30 years old, a citizen of the United States for at least 20 years, and a resident of New Jersey for at least seven years.
Lieutenant Governor of New Jersey
least 30 years old, a citizen of the United States for at least 20 years, and a resident of New Jersey for at least seven years. 
what are the duties of the lieutenant governor of new jersey? To be the head of a cabinet-level department or administrative agency within the governor's administration.
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Lieutenant Governor of New Jersey [SEP] Qualifications and duties
As amended on January 17, 2006, New Jersey's state constitution mandates that a person may only be eligible for the position of lieutenant governor if they meet the eligibility qualifications to serve as governor. Article V, Section I, paragraph 2, requires that a candidate for governor (and thus lieutenant governor) be at least 30 years old, a citizen of the United States for at least 20 years, and a resident of New Jersey for at least seven years. Within 30 days after the certification of the statewide primary election, the candidate for governor selects a running mate to join his or her ticket as the candidate for lieutenant governor.