Q. Thank you and Rav Miller for your prompt answer to our last Shaileh. A client is interested in buying a Dollar store, there are items that are part of the inventory that are not Kosher such as cans of prohibited fish and spam, is there a problem with selling them? The customers are not Jewish.
A. In principle there is a prohibition on trading with a "Dovor Hoosur" (prohibited foods). Some Poiskim maintain that the prohibition is rabbinical, (Bais Yosef, Rashbo, Y.D. 117 et. al.) since he may come to eat the items he does business or work with. Other Poiskim assert that it is biblically forbidden (Tosafos Pesachim 23,a - Rambam- Rosh - Taz Y.D. ibid.). You may trade, nevertheless, with foods that are only rabbinically forbidden (Y.D. ibid. 1). Accordingly it would certainly be advisable not to engage in a venture where you would have to do commerce with biblically prohibited food. However if the store was purchased, the non kosher foodstuff that was acquired with the rest of the inventory, could be sold but not reordered. (Y.D. ibid.)
However, the Oruch Hashulchon (Y.D. 117,27), seeks leniency for those store owners that have as a small part of their merchandise non kosher foods, since the items are few, and their main business is conducted with permitted foods. On condition that maintaining those provisions are essential for the success of their trade.
Horav Shlomo Miller Shlit"a, advised, in addition, to sell to a Gentile (in a halachically permitted and proper manner), that part of the business that deals with non kosher foodstuff. He further required the Jewish store owner not to handle or be in direct contact with the non kosher items.
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit"a