wait until it is completely paid off or get something as collateral it would be very easy for someone to forget to pay you after they have received the item
You wait until they pay all the payments, it s the same thing as if you were to put a item on layaway you pay it off first then you receive the item, but make sure that every payment they give you make sure to give them a receipt on every payment they give you.
Wait until the necklace is completely paid for, BEFORE you release it to them.They may make one payment, then not pay on it again.Then you are out your money and your necklace.