Etsy and craft fairs were my first 2 thoughts when you wrote that you wanted to do the fondant toppers. With so many party packages popping up on Etsy, it seems the trend right now is for a semi-DIY approach. When it comes to cakes, this means more moms may be baking cakes/cupcakes but want a more professional look when it comes to the decorations, so they need something premade to arrange themselves.
Renting a commercial kitchen could be a possibility if you wanted to avoid the hassle of home inspections. Some cities have kitchens specifically for renting, but I've also heard of people renting church kitchens or small, family-owned restaurants/bakeries that could use the extra income.
I imagine it could become a career if you explore various places of selling/creating. You could do contract work for local bakeries or cake decorators -- you do the work that they don't have the time or skills to do. Also, at bakeries with storefronts, you could possibly sell items on commission, like having fondant toppers for cupcakes that could be packaged and sold individually. I work in a bakery, and I'm asked almost daily if we have anything to put on top of a cupcake for a last-minute birthday gift.