Verifying income on a new park

my wife and i are buying another park. its just a small park, 14 pads, and the current owner is just a mom and pop operation. half of the tenants pay in cash, and the others pay by check. they have a lot of other properties so there is no way to verify the income off the tax return, and expenses are all mingled in with the other properties. He keeps no records on the park. My bank wants to see expenses and income records and i am not sure how i can provide them what they need. The cash, while nice to get, sure does make the financing hard to get. Any input or opinions would be greatly appreciated.