So I see a lot of the obvious solutions but nothing that actually answers the question. Let's get practical.
Ground rules, in this hypothetical scenario I'm working under the assumption that you are not going to persue the obvious legal requirements and instead are looking to keep the suitcase money (we will be calling it S$ for short) without potentially getting trouble.
Step 1: Don't fucking touch it
!First, verify that It's an amount worth the trouble. If so, don't spend it, don't play with it, don't even look at it. Put it, case and all into a vacuum storage bag, put that bag in a metal container with a lock, put that container somewhere inconvenient but accessible. You're going to pretend it doesn't exist for at least 3 months, Ideally 6. If anyone can connect it to you, it won't take half a year for them to come collect. If they come, hand it over with absolutely no argument, no questions, minimal conversion. You don't know what it's about, you don't care what it's about. Inform them that storing their money in vacuum bags between clothes and transporting them via generic hiking style backpacks will prevent this from happening in the future. It isn't as stylish as they briefcase of bills, but it's harder to steal, drop, or spot in a crowd and healthier for your posture.
Be amicable with their demands, let them count it there, answer any questions they ask honestly, offer them food or alcohol. You were keeping the money safe to see if anyone was coming for it before you kept it. You can't call the police when they leave because then you'd have to explain why you had the money and didn't report it, they have the money and killing you would just increase the risk of getting caught. Everyone walks away and forgets this happened. The food and drink will calm your nerves in the stressful moment and works as a social lubricant, theyre less likely to kill you for this if you're cool, friendly, and hospitable.!<
While you wait, you don't have to be idle. 6 months is plenty of time to establish a cover story and a budget. The cover story is how you prove this money isn't a suitcase full of bills you happened upon, it's money you earned legit. A budget is a budget, you should already have one at home this is just bigger.
Step 2A: Money is math
!The method we will use here depends heavily on the amount of money so we start with budget because it's basically the same any way we cut it. There is a big caveat. Depending on your income, there is only so much you can excuse before someone takes notice. We don't need a rags to riches story catching the attention of interested parties. Most of us can disappear between 10k and 100k, but if you're not already in the big bucks, explaining a million dollars in your lifetime is not convenient without a rich uncle to bump off. Fortunately, at that kind of money you can just find a quality lawer and financier. So do that and pay them to turn your egg into a golden goose.
Start by figuring your income and expenses. We'll be using this to establish realistic projections for your new "income." After all, if you're making minimum wage working 80hr weeks, it's going to look bad to report a sudden double in your income that's straight cash. If it's a job that pays equal for the same hours, that only leaves you 8hr a week to sleep. If it pays better for less hours, why aren't you working there instead? Ideally to start you want to allow for a quarter of your income in suitcase money. You won't need to explain having a side hustle that gives that. Put it in the bank and try to save this money, we're building a papertrail to legitimize your new "career" move.
The idea here is simple, but it takes research and math. Based on your cover story in the next step, you're going to establish a modest trajectory. Average out the kind of money you can make doing the thing, divy the S$ into monthly amounts that are slightly below that trajectory. Do not make them even amounts, do not make them consistent amounts, do not make them silly patterns. If you're up to it, break it down to change. Seal these in vacuum bags with printed labels for the date each one is meant for. You don't want to accidentally deposit a higher amount than projected. Ideally, transport each one individually to a safety deposit box, store them in a fire safe, burry them in a trunk in your crawlspace, just make sure they're safe and hard to find. The worst thing would be nosy family finding your stash or losing it all to a random electrical fire. !<
Step 2B: Find a clever disguise...
!Now that we know the shape of the beast, we need to find its name. You're going to want a very boring or even cringy side hustle that is cash oriented. Landscaping, basic car maintenance, collectables, vending machines, these are things that don't have a high overhead, don't need good records, and can scale realistically to the values we'll be using. Equally important, it needs to be something you're interested in. If someone audits you, you have to breathe, sweat, and bleed this topic. It's going to look pretty bad if you grassroots a business based on antique toys and you can't tell the difference between Fisher Price and Playskool.
The next big step, actually do the thing. You don't have to make a profit off of it, 80% of your monthly "earnings" is vacuum bagged and waiting to be deposited, but you fo have to engage in it. How's it going to look if you made 2k mowing lawns and no one can say they've hired you? You own 40 vending machines and no one has ever seen you refill them? That's dubious. !<
Step 3: Establish ownership the easy way
!Ideally after 6 months you can safely say you're in the clear. Now you can start the hard part. If the money is around 10k-40k and you don't have any pressing needs you can play the slow game for an easy score. The IRS allows you to claim 10k annually as Hobbies before they tax you as income. Do the hobby, deposit it like a side hustle, claim hobby and in the next 3-7 years you'll have put all of it in your bank account without ever having to explain your sudden interest in Alpha edition magic: The Gathering cards. Just follow a steady curve of profit until your "declining interest" leads to a pittering out at the end of your S$ or you actually make it onto a profitable venture.
Now if the money is bigger than that but not quite buying a senator money, you're going to do exactly the same over a longer scale with bigger amounts by establishing an LLC, operating a business with low expenses and cash heavy transactions, and claiming the S$ as your monthly incomes. You're going to be looking at gas stations, small theatres, car washes, laundry mats, smoke shops, home repair, cleaning, or no tell motel, avoid anything with more expense than you have S$. Incorporate after the second year, that way if the business never manages to float without the S$ you can write it off and burn it down when you're done!<.
Now obviously I can't condone this kind of thing in real life, but if you're ever looking for a business partner in a hypothetical scenario, jit me up.
