Almost all of the ideas on this thread are quit comical...no offense, I know most of the bros are just throwing out ideas.
I'm not a commercial grower, but i know business. I've made money in Real Estate, investment banking and merchandising. First thing, if your lifestyle doesn't reflect your income, big time red flags will be raised (if you're a target of an investigation). So paying your bills with employment income and supporting your lifestyle with cash is never going to work in the long run...too many loose ends.
The best way to turn cash (regardless of where it's coming from) into legit wealth is in Real Estate. I've personally flipped 5 houses (legitimately). Here's how it goes. You buy a house as your principal residence that needs repair . You hire contractors to make repairs and pay cash for most (but not all), only you are the guy who did repairs as far as anyone is concerned. All materials are bought by you and you keep receipts. Over the span of 6 months or a year, you put a 100k into your house, of which 2/3 is labour and you increase the value by another 100k or more. Profit will not always be the same...but your investment will be reflected in the new value of the home. You sell the house and make your profit. You move onto a bigger project and so on. In 5 years you create a million or more from your Real Estate venture.
Keep tools in your garage and learn a thing or two about the reno business. When you sell your house, all funds are managed by Lawyers and your bank is in the loop.
The plan is fool proof not withstanding a few mistakes along the way. It really doesn't matter if the cash you are using comes from legitimate sources or not, there is no way for anyone to know, because you did the work yourself and the proceeds are as a result of sweat equity.
As mentioned, I've already done this with legitimate funds and actually did most of the work myself, but no one would have known if I hired out some or all of the work.
Clearly this strategy does not provide instant results that many may be looking for, but if you think like a businessman rather than a person with a hole burning in their pocket...you'll succeed in the long run and your wealth will be legitimate...
Hope this helps...
Cheers...