I find that curious - how many is "a lot" of calls? You have a much larger population than I do, but I've never even once had anyone ask me about repairing a camera - even back when everyone had one.
While there's still a market out there for dedicated cameras, it's certainly a small fraction of what it once was. The trick as always is how to target that niche market in a way that makes it worth your while.
A quick Google reveals at least some availability of parts. Here for instance:
Nikon Camera Repair Parts Same guy has Canon, etc.
So it looks like it might be doable if it were worthwhile. On the upside, people can live without their cameras for a few days whereas phones & computers are like oxygen. So you'd be able to take the time to research the parts and disassembly at comparative leisure.