Chametz After Pesach

Question

Kavod Harav L'chatchilah, how long should one wait after Pesach before buying Chametz products from a grocery store that was owned by Jews during the holiday and chametz there was not sold? If one buys products before the stated time, should one wait until the passing of the permitted date to eat the products? Briefly, is the halacha that one cannot benefit at all from those specific products owned by Jews during Pesach? Todah Rabah.