your work is lovely. You clearly have a good eye and your compositions are quite nice. You've got the "photography" part of the business down pretty well but IMHO you'll have to figure out how to do "studio" work as well with backdrops and lighting.
As for the business side, that's the whole game. Being a great pet/child portraitist isn't going to do you much good if folks don't know about you. So, marketing is the key. And then there's all that stuff around pricing, production and delivery of the final product. Dabbling in it is fine. But if you want to make it a business, you'll have to put in the time to actually run it as a business. Good luck. If you need advice, this is the forum where you'll get it.