"Alfred Hitchcock Presents" The Orderly World of Mr. Appleby (1956)

Mr. Appleby's antique shop is losing money, because he is so fond of the best items that he refuses to sell them to anyone. A representative from a supplier visits the shop, and tells Appleby that he must pay his bill within two weeks, or else the supplier will reclaim his inventory. Appleby's wife has a moderate endowment, but she will not help him, so he kills her and makes it look like an accident. He gets away with it, and marries a wealthy woman whom he had met in the shop. But he soon learns that she knows all about him, and has made careful arrangements to protect herself.