You can be anything you want to be the second you put action toward it. If you’re an artist, you’re an artist whether you’re good at it or even if you just decided to become one this morning. Who are the referees? When you decide to become an engineer and start taking steps to learn programming, you are in fact an engineer. You’re a pretty bad engineer, but that’s only because you lack experience and any skill. You’re an engineer at the beginner level. You aren’t good enough yet to get paid for it. There’s also no official ‘moment’ you become good at anything. My high school astronomy professor is pretty good at space-talk – until Neil deGrasse Tyson walks in. These things are relative.
You are whatever you want to be the second you start. Official titles are different. Those are credentials to function externally, and you’re probably not ready for that.
Becoming something is the process of passing into that state. You’re always becoming something. You become a better artist, executive, or software engineer. Or, you become a worse something because you don’t practice. Or you can become something else entirely. It’s up to you to decide.
Some of us were born human beings. We can decide what we will become. That’s what’s special about being human. A potato is alive just as well, but it has no choice other than to die and get eaten. You can choose to die and get eaten also. You can even choose to live and become a poet.