Off hand, I'd say a home garage is a bit small. I'd wonder who makes the molds and stores them. If this is a hobby and you're willing to pour money into it, there's no stopping you from trying. If you plan to start a business, that's another issue. I do know a fellow who started a special metals business in his garage and now owns a very large building with tons of heavy equipment. He mainly does custom stainless steel and aluminium work and uses laser cutting machines that require a lot more electric power than you'll see in any garage. He also employs several people including some skilled welders but it did all start in a garage.
This goes a bit beyond the standard forum topics but I was curious if anyone knew of an affordable way to set up a home plastic injection molding operation. I know about 3D printers but I figured an actual aluminum or steel injection mold might offer a better variety of materials with which to work. Is this something that's just way too ambitious for a home garage?