Ask HN: Can we create a homebrew chat GPT?

As impressive as ChatGPT is I feel queasy that it is owned by one company and we cannot run it on our local system. We cannot inspect it, modify it and own the model ourselves. That brings me to my question. Is it possible to create something like this ourselves on our own local system? Or does it need too much GPU power for it to be feasible to be created at home?