I'd say go for it and good luck if you decide to!
Granted it always costs a lot of money to start up any business, but if you balance your time, money, and effort properly you can succeed on a budget.
I'd say there will always be a need for retail. If you can carry the right products, animals, services, and find a good location with a nice customer base around the area, I think you should be absolutly fine.
But I can agree with most others that it's a tough operation to pull off with still offering low pricing with the overhead of owning a retail shop. But I think it would just depend on what you are carrying and breeding on your own (breeding mice and rats is a great + for a pet store, even for pets and not just food). There are many other things aside from exotic reptiles, such as Aquatics, Small Animals, Dogs, Cats, etc.
I can tell you there are millions of people that spend unimaginable amounts of money on their pets, especially in the dog and cat area.
Anyways, good luck!