Learn to be a roofer, make bank (I paid my ~"uneducated" roofer like $5k for labor alone for ~48 hours of labor), buy rural Indiana land, build your own private observatory, enjoy doing your own research without the crushing burden of the academic grinder.
Astronomy is one of those fields where amateurs make new discoveries quite frequently.
You can't do private research because most astronomy is really data- and compute-heavy astrophysics. Optical searches are fun and everyone loves new comets, but comet hunting isn't academic science.
Interestingly, when hunting on a computer or some new celestial object gets "hunted" by university astronomers, they call it "research" and don't smugly dismiss it as just some fun that can safely be gatekept from being called astronomy.
As always, when working outside the system, it should be expected that semantics will be used against you, but if it's your interest, it needn't stop you nor need care about such unpersuasive arguments.
Hmm, so, there's a teenager that loves astronomy and is very clever but he lives in rural Indiana with some parents who neglect him.
(Or any third-world country around the world; or even worse, a war ridden place).
How do you suggest he should prepare for this kind of opportunity?
I'm not detracting from his merit, but 99% of this outcome is due to being next door to Caltech and sympathetic to its faculty.
You don’t choose what you want, you choose what you can have.