I just had a possibly-brilliant idea, but I am completely not an expert in retirement/tax laws, so I'm wondering if there's anything I'm missing here:
I have a regular job I plan on keeping long-term; it makes enough money that I feel comfortable maxing out my 401k, which is great. I also max out my IRA (Roth, though for the sake of this, I'm not sure that's relevant), and I'd love to contribute more tax-sheltered beyond that, which until now, I believed was just not possible.
However, I also have a significantly smaller income stream from a side-hobby - but big enough that I would totally get in trouble if I were to fail to report it (on the order of a couple thousand dollars a year or so.) I just realized - as far as I can tell, the only requirement to being able to open a Solo 401k (Roth or otherwise) is that you make reportable income from something that is not from a job that provides a 401k - and that you can then have your "employer" (i.e. yourself) contribute extra? Can I actually contribute my full contribution to a work 401k, but then have my side hobby "contribute" into a Solo 401k via "employer" "matching" of a few hundred a year extra (as it looks like you're limited to 20% of what you earn?) Granted, that's not a huge amount of money, but it's not nothing, either. (And would mean if that side income ever grew larger, I could start "matching" more money, too, if that's actually how it works.) Even better, presumably that would mean I could also contribute the full amount I made via the side-hustle as well, if I reduced my contribution from my work 401k commensurately, for more direct control over how it was invested? That'd be great, too.
Am I missing anything that would make that not work?