Anyone in the business of buying gold, silver, platinum or palladium for its melt value must register with the police of the town where they do business, post their name, address and per-weight prices where you sell, and weigh your metal in front of you on state-certified scales. They take proof of your identity, give you a numbered receipt listing each metal, its fineness, weight and price, and keep that receipt and digital photos of the metal for a year. The metal stays in the form it was bought for at least 2 business days (48 hours minimum). A transient buyer, meaning one that has not been in retail business continuously for at least 6 months at the address where it registers or plans to close within 6 months, must also post a surety bond with the state Office of Weights and Measures (N.J.S.A. 51:6A-1 and 51:6A-5).
Jewelers, wholesalers and smelters who buy used jewelry have a second set of rules. They check a government photo ID, keep your name, address, phone number, a photocopy of your ID and photos of each piece for 5 years, and send the police a weekly list of what they bought. Each piece stays in their possession for at least 10 business days after that weekly report is delivered, and anything that looks stolen must be reported to police right away. Licensed pawnbrokers fall under a separate pawnbroking law.
Neither law sets a minimum seller age or limits how a New Jersey buyer may pay you.