Well anyone can 3D print something, but it’s the modeling of a printable object that is your skill. However modeling and designing are two different things.
If I had your equipment and skills right now I would start printing bathtub jet plugs. Convert a jetted tub into a non-jetted. Probably only a few different brands and designs to cover.
Aside from that, I’d get into mold making. You can 3d print a mold, or even a mold of a mold. Or a mold of a mold of a mold. Then you can cast objects in metal or ceramic, or silicone or even plastic (haha) or other materials that can be a liquid. Way more interesting than plastic shapes. Plus molds can be used many times.
As far as the business goes? No idea. Start by making useful objects that people want to buy. But that’s kind of a different skill of “inventor”.