Simple yeah, but worth anything? If you pay taxes when you receive and taxes when you sell it, what does that leave you with? 30% of the actual mining results? Bleh.
Reminds me when I did some adjunct work in addition to my normal job. I loved it, but the pay was completely union negotiated and they can never get tech people in to teach the tech classes. I thought the pay was pretty OK, especially as I picked up enough classes to go from per credit to a part time salary.
I know how taxes work, generally speaking. This still was a shocker to me.
I didn't realize that (and this is common sense in retrospect) they weren't withholding enough at the schools where I was teaching, as they were only withholding as if I had only that income. Same for my main job, but I was already tweaking dependents and stuff there. So I made lets say an extra $12k (after "taxes") in the year for teaching two nights a week for a handful of months. Not bad, right?
What was bad was when they came for $5k in taxes in April because I miscalculated. And there was penalties because of how short I was. And I know had to file the next years taxes quarterly (got that removed, as I remember now, somehow) because I had shown how ill equipped I was at paying my payroll taxes (I maintain this is something the HR department who hired adjuncts might have wanted to mention since they were headhunting people with jobs.)
All of a sudden I realized that I was getting ~60% of the advertised pay (I know, no surprise had I rubbed some brain cells together) and I realized why they can never get adjuncts in the industry to teach because they can't adjust their pay to be worth it when you pay taxes along side other income.
Anyway, I am much more leery of the tax implications of new income sources now.
About expenses - if you are already claiming your home office (electricity and sq footage and all that) and internet as unreimbursed expenses on your taxes, double claiming them might start getting dicey. If you aren't already claiming them, why not? American tax law here though