​I have created a Rental Application  to add product for rent for duration like hourly, monthly, etc. But when i add product only the product which are available for sale are listed in Shop. I think it is due to sale_ok field in product.template table. Because i have made updation that both sellable and rentable product should have is_publised field to True. 
I want to update the product domain such that the product having field is_Rent=True should also be listed in the shop page. I am unable to locate the folder where this product domain is defined that on sale_ok=True the products are displayed. Please solve my issue, in which directory i need to make changes.