You could have an old school exchange where people go in person to shout bids and offers and settle with briefcases full of $100 bills. Those can be used to pay accountants, utility bills and property taxes.
In case anyone is wondering, this is money laundering, and if you wind up with the wrong person on the other side, getting arrested and charged is among the better outcomes.
Running a legal porn site isn’t illegal.
I assumed that wouldn't be necessary if not operating like a business with the intention to turn a profit. If I sold my car for cash, would I have the same responsibility?