The next thing to consider, if you have selected a clinic that you will visit rather than a vet who visits you, is the waiting area.
Is there a separate waiting area, or do you go straight to the exam room? Are there separate entrances and waiting areas for dogs and cats? Will the resident cats come visit you in the waiting room? When your exam is complete and the time comes to pay, is the cat still in the exam room with his human, or must Kitty go up to the front counter in the waiting area? Is there a counter by the reception desk that is not quite in the waiting area? Do they require that pets be in some kind of carrier or on a leash, or are pets in their human's arms accepted?
At the vet Parker currently uses, they can take some payments right in the exam room. For other forms, they can take the card to the front while the animal stays in the exam room. Sometimes, however, the animal goes to the front and stops on the way out. Will they let the human put the pet in the car while the payment is processed? (for humans traveling alone with their pets, that might lead to an animal in an extra hot/extra cold vehicle, which would not be ideal).