Bob says to Rob: "I offer you $1,000 for this thing".
Rob replies: "I accept your offer".
From this very moment, is Bob the legal owner of the thing? Or does he need to wait for the occurrence of payment, payment clearance or delivery before he becomes the owner?
Bob and Rob are both private individuals who do not know each other other than for this transaction. Rob is not a store, he is just a one-off seller of the only thing (which he owns). There is no written agreement.