Business Data 1
---Product A
---Product B
Business Data 2
---Product A

Business 1: Joe's Plumbing, located at ... ... ...
---Product A, standard ad appearing in category 3, with text "awesome plumbing"
---Product B, cooler ad appearing in category 9, with text "cheap plumbing"
Business 2: Joe's Burgers, located at ... ... ...
---Product A, standard ad appearing in category 4, with text "zzz"

class Business(models.Model):
    name = models.CharField(max_length=255)
    address = models.MagicAddressField()

class Ad(models.Model):
    category = models.ForeignKey(Category)
    text = models.CharField(max_length=255)
    business = models.ForeignKey(Business)

class Ad(Product):
    objects = ProductManager()

    category = models.ForeignKey(Category)
    text = models.CharField(max_length=255)
    business = models.ForeignKey(Business)