Yes we have several 3rd party agreements.  The main advantage is that they originate the orders and communicate them to us electronically.  The sale is worth some money, especially on a rainy day when no one is coming in but we are still receiving several 3rd party orders.  Also, phone orders take a lot of time, and having someone there to deliver it quickly can take time as employees are often in the middle of other tasks.  
To me, a partnership depends on how flexible the relationship is, and any time you sign someone else's contract, you are making money for them, but you have to be careful to ensure you are profiting.   Overall, it is a small profit margin.