My .02 cents worth, open a pawn shop. Lots of opportunites to filter your cash through the mix.
Travel. No one in Argentina will care and no one in the US will know.
Mark Sanford would disagree. 
So, what would happen if you DID just walk into a bank with a million bucks, and said “deposit this, bitches!”? If you legitimately found the money, they can’t prove that you’re trying to launder it because you’re not.
Why not just deposit the money in the bank, fill out the forms, declare the income to the IRS, pay the taxes, and go about your business?
Right, they’d just file a CTR. The IRS would take notice in that case, but if it was right there on the old 1040, the IRS would be happy. You’d pay like 35% Federal taxes, plus whatever State income tax they have there, say maybe 10%, so 45%, thus 550K left over. Only worry would be someone at the bank gossiping about it. For that reason, I’d deposit $100K in 10 banks- not close to where you found the cash, next town over, filing a CTR each time, reporting the total on the 1040. In fact, I’d have some checks in the mail for $200K for Estimated taxes a few days later.
He came back, classic mistake. 
Very easy if you have an account of, say, 500k in Bank A.
Withdraw the money, go deposit it in Bank B. You tell them it comes from Bank A. They check. OK.
Then deposit your booty in Banks C and D. You tell them it comes from Bank A. They check. OK. 
Or a strip club.
Do the feds and IRS only get interested in cash deposits over 10,000 dollars at a bank? What if it was an unexplained check for 10,000 from say, online gambling? However the check is through a clearing house so the bank actually has no idea what type of transaction it was. Assume it clears with no problems. Are they likely to report it?
I’m not proposing this as a solution, just curious how much attention it would garner.
Instead of STARTING a cash business, I would contact someone who already HAS a cash business. He puts me on the payroll, and every two weeks I give him, say $3000 in cash and he gives me a check for $2500. I can show legitimate income and he mixes in the cash with the rest.
My worry about doing it that publicly would be not so much that someone would have a legitimate claim to the money as that someone would have a much less than legitimate claim to the money, and still choose to exercise it.
Where I think more than a few of you are going awry is with the apparent intent not just to keep and spend this money, but to multiply it. More than one lottery winner has ended up broke when he thought his winnings were his ticket to high finance. Alas, having one wild stroke of luck does not make a fellow a financial wizard.
Why not just get money orders here and there, $150 or so at a time, using 7/11 stores and check cashing sites? I’ve seen people buying boatloads of them in line - even making them out to the electric company and other utilities. I guess they make you do that if you bounce a check?
I think you could make a monthly trip to several different stores, and get 3-4 of the same money orders each time with no trouble at all. You don’t have to put down who it’s made out to.
Or purchase traveler’s checks at different banks each month?
CTR is only for cash. If it’s your first one, the feds may look, but the CTR is in suspicious activity in itself. If a bank officer thinks you are intentionally avoiding the CTR, e.g. deposit of $9999 or somehow determine you made two deposits in two different banks summing to >$10k, then they will file a Suspicious Activity Report, and the gov will take greater note. Otherwise, depositing $10k could be gambling money or it could be illegal income; if it is way out of an individual’s typical behavior then it’s worth taking note.
Online gambling is still technically illegal, right? I assume the check is cut from a generic-sounding company. A bank would almost certainly not care where it is coming from, but may put a hold on it if it sounds risky. That is to cover their own ass in case of default and not a governmental regulation.
I’d try the business laundering angle. I paint and occasionally sell gaming miniatures, for perhaps a couple of hundred of dollars a year. After finding this money, I’d go to gaming conventions as a vendor and do a couple of thousand dollars in transactions at each. Then legally report it as income. Same with commission painting, which has the added bonus of not having to supply the miniatures in the first place. I would not be excessive in my “earnings.” I’d keep my career and just use my “side-income” as a supplement.
And lots of foreign vacations where I could spend even more moolah unnoticed by the IRS.
When I worked in real estate, I saw people with bagloads of cash. Do you think people who rent thosde $5,000 one bedroom apartmens use legal cash.
If I ever find that million dollars, I will continue to live my present lifestyle. If I get called on it, I will tell the government that I am being “kept” by a big name person with a family image. I will describe in great graphic detail the bizarre sexual things he makes me do. (I understand there are websies that will help you with this). If they ask who the person is, I will say “If I tell you, I’ll be killed.” I’ll say the money is technically not for the acts, but is always given at the end for a thank you tip.
Money orders above a particular amount require ID, but last I checked that amount was $950 - which is luckily my rent.
I’d get into the house concert business, hiring favorite performers to play in my living room before a small group of invited guests. It’s an almost entirely cash business. The performer gets the entire amount collected, the “promoter” gets the unique pleasure of live music in their home. Pay them in cash and it travels on to the next town. I’d have a very nice sound system and recording equipment (all of which can be bought piecemeal on-line with money orders or cashier’s checks).
Pretty much my thought.
But before… I’d move to a state with no personal income tax. 
Oh, If you buy money orders or cashiers checks for over $3000, then you run into the same problems as $10,000 cash. Bank officers have to do a Monetary Instrument Log (MIL), and will file an SAR if they think you are being sneaky and avoiding being reported.