I have never hired with a friend however I think the situation might not help you create the perfect situation. When I think about it, the feeling that are making you uncomfortable in the first place will still be there. The addition of a friend won't really erase those feelings and although it may layer on a certain voyeuristic element at the same time it may add other feelings you are not aware of now. For instance, are you and your friend planning on having sex or are you just planning on watching him have sex with the escort? Depending, have you had sex with your friend before? I just think you will be adding so much to the situation that it won't make you feel any less nervous. As someone already wisely mentioned "making sure YOU are feeling comfortable SHOULD be a priority for a skilled/responsible provider."