Pet Photgraphy as a Business?

Our rescue has a very close relationship with a local groomer who gives us a good break on grooming our rescue dogs. I give her the dog rescue calendar I do each year as a thank you. She keeps trying to convince me to start a pet photography sideline but, I a so busy with my rescue work (both the photography and the other time consuming rescue efforts) that I don't feel like puting anything else on my plate...