But you can train a small LLM with a gaming graphics card -- I managed one on a GTX 1660. I don't think pg is suggesting that you try to chase the frontier. It's more like building your own OS in the 80s, or web server in the 90s -- sure, you'll never match the commercial offerings or the big OS projects, but building something from scratch within the limits of the hardware you can afford is amazing educationally.
"I'd build the foundation of knowledge to base a startup on later"
what kinds of startups ?