Im Irish and we wont ever have a scarcity of water, lol, its rains like 80% of the year here and theres basically no pollution (compared to say larger countries) to dirty it up, so we'll always be grand.
You know the downfall of hydrogen fuelled stuff? It never gets enough research because its too efficient. Hydrogen fuel cells for example basically make free power if you have water and sunlight, problem with it? Big one off cost, but once its running the power it produces is free and a contained fuel cell generator? Its basically a solar powered high electricity output self contained system. Research it man, hydrogen is the past, present and will be the future.
But back to the original topic and completly theoretically...you would need a cash business that trades in a service. Something with low inventory and a high cash value. Valet service is one example, for a cost to you of just time and cleaning chemicals people will pay like $200 for a proper valet. How many of those per week do you think you could theoritically do? I think the trick is to actually run the business, just not pro-actively seek customers, but a few is a good thing. That way you can put the dirty money in with the clean money, no proof of where any of it actually came from and legitimise it by paying tax on it all as if it were all legimitate income. Hell that way the IRS auditor could even get you to valet their car if they want proof. And who knows, if you actually run the business well it could grow and you wouldn't even need to grow pot for cash anymore, just for stash if you get enjoyment from actually just growing it.