Can you use cash for down payment if it hasn’t been in the bank for 2 month

Hi search funder
I was asked a question, about debt regulations around showing where the down payment came from.
The construction business owner was being paid with cash in some instances for his work. The owner kept the cash vs depositing it in the bank after paying his workers. Now, he wants to buy a business; he has the Downpayment requirements, but it wasn’t in his bank showing two months residency . Is there a way to work through this with the banks? Some of it was from jobs years ago, he would have to try to find invoice’s. He is an old school thinker in terms of not putting all his money in the bank. Any suggestions would be helpful.