What is the ruling on opening an online store to sell food, supplies, and accessories for pets, given that the food may contain animal products from unknown sources (possibly pork or carrion), and that the supplies include cages, collars, and other items?

It is permissible to sell animal feed, even if the buyer keeps animals for an unlawful purpose, unless it is known that the feed contains unlawful ingredients such as pork or carrion; in which case, it is not permissible to sell it. It is permissible to sell animal supplies, except to someone who is known to be using them for an unlawful keeping of animals, in which case it is not permissible to sell to them, in order not to aid in the unlawful act. However, if this is not known, the sale remains permissible in principle.