Actually, what you're talking about is skimming - kind of the opposite of laundering. In the classic money laundering scheme, the owner already has the cash - from an illegitimate source. Now he needs a legitimate business to run the cash through to make the cash legitimate. The car wash is an excellent choice as there is no direct tracking of the number of customers through cost of goods sold. So, the business does a huge cash business with no customers and the regular business mostly through debit/credit/zelle/paypal/whizbang/hoohaw payments. This gets the illicit cash on the record and in the bank. Anyway, I read about this in a book...