> a 21-year-old software developer In the past I have seen self-certification for Accredited Investor status, as well as out-sourced services that verify some data for a determination. I think response around what is legal or not is best left to those with a background and education in the legal profession.
> what is legal or not is best left to those with a background and education in the legal profession Tangent, but I just want everyone to recognize how obscenely absurd this (largely true) sentence is. How are we, the vast bulk of non-law-school-graduates, supposed to follow the law in our day to day lives if just figuring out what's legal literally requires multiple college degrees?
The reason lawyers get paid so much is that if you're doing something that is right on the boundary[0] then the difference between legal and illegal might be extremely fuzzy, and also worth a lot of money, so it's worth paying someone $1000 an hour to write a long brief in your local judge's preferred WordPerfect template about why what you're doing is OK.
On the other hand, the SEC website linked by OP just has a checklist of Accredited Investor qualifications, and it's possible to read them. Do you have a salary of $300,000? You qualify. Did you make $195,000? Well, that's less than $200,000 so unless one of the other checkboxes matches, you're out of luck[1].
[0] Maybe it's illegal by the letter of the law but you think it shouldn't be, like ride-sharing in locations with taxi regulations. Or maybe it's not illegal but might be viewed with extreme skepticism by regulators, like offering a non-fraudy Bitcoin exchange. In both of those cases, there's an easy solution (just don't do the maybe-illegal thing) that is accessible to the layman.
[1] Maybe you can hire a lawyer and/or CPA to get your $6000 of undeclared dog-walking income counted for the purposes of Accredited Investor qualification, but is it really worth the hassle?