I was good friends with a guy who owned a pet store. It was very difficult to make a living with it. However, with that said, if you are creative along with good location and business plan it can be successful.
He made most of his money setting up fish tanks for businesses. Doing grooming for dogs can be very profitable also. I believe that Petsmart gives about a 50% commision to the groomers for each pet.
Also, have many special events to get people intrested in your store and to get local media attention. These could include free adoptions, halloween costumes for days, free 15-30 minute training courses, etc.
With hard work and some brainpower, it can be very successful.
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