You could get a 100W solar panel, mount a Bitaxe (or two) on the underside. Add a battery with charge controller so it won't cut off when a cloud passes over. Throw it on the roof of your house (unless you need a permit) or build a stand to keep it off the ground. Wipe the dust off when the output drops too low. Could probably build this setup for less than $300. Option to add more batteries/panels to get it running 24/7

Assume you average 30W of generation (assuming 80% efficiency and 12 hours of no generation at night), then you'd rack up 21.6kWh of generation over 30days. Assuming you would have paid $0.16/kWh for grid power, that's a savings of ~$3.50/mo

However, the bitcoin network won't pay you $0.16/kwh (especially with a bitaxe). You'll be lucky to get $0.05/kwh

So a $300 setup would "pay for itself" in about 7-21 years (depending if you count "savings" or "income" as your ROI).

However, you'd learn a lot about electricity and some people pay $50k to a university to go do that, so it could be a massive opportunity depending on your goals!