I'm not all that familiar with "this industry" - but I am somewhat familiar with the common issues that self-employed artists run into, and these issues are common across all media. Pixel art, like other art, is skilled work, but a lot of clients try to treat it like it's not when it comes to paying for it xP
Pixel art is a bit niche, so it might not be easy to find pixel art-specific work in general places like Upwork. Sites like that also essentially put you in competition based largely on price, which is not great for getting you paid fairly and for helping you find the best client for you (and vice versa - making sure you're the most appropriate artist for your client). Most pixel artists seem to get their clients though specialist communities and personal connections. You can and should still make a listing there, but make sure you also post in the job/portfolio sections of Pixelation, TIG Source, Pixel Joint, and other places frequented by people looking specifically for pixel artists.
$12/hr is very cheap, so I'd say that's a good bare minimum to start with. No need to wait, as this isn't about being legal - as a self-employed person, you don't have a legal minimum wage - it's about making sure your time is adequately compensated. If you can't earn enough with pixel art, there are probably other things you can do, possibly even more in-demand things than pixel art. They might be less fun, but desperate times call for desperate measures, and you can always return to pixel art.