lay-by

Procedure of a Lay-by sale

Q: A person wishes to purchase some goods from a certain furniture store but does not have the money at present. The seller tells him that he can buy the furniture on lay-by. Will it be permissible for him to purchase the goods on lay-by and how does lay-by actually work? Through lay-by, does one become the owner of the goods immediately or only when the goods are completely paid for?