I bought one a long time ago that way. The financials were just had a handwritten ledger because multiple washes had been co-mingled in the bank account the owner had. The person was a friend and I had no reason not to trust him. I spent minimal time investigating the revenue, kinda managing the place for a week or two but as we all know you can have unusually slow (or busy) weeks with no real explanation why. Anyway, I made the purchase. It took me a couple for Months to realize I got screwed. Revenue was probably 30% lower than anticipated. What I thought was going to be a way to earn a decent living with one wash turned into a wash that just cash flowed most Months the first few years.
I heard (second hand) of a situation in a neighboring state where a person bought a wash from a multi site operator that also had other businesses. The operator took income from his other business and deposited them into his car wash account to show income to potential buyers. The buyers managed to get a settlement against him.
The lesson I learned from my purchase is don't trust anything but tax returns and bank statements from all related properties that put all the numbers together. There is no reason for an owner to co-mingle funds of multiple washes into one account. Anything else that is purchased is based on value of the land and improvements, plus any value I can add.
Nowadays with 80% or more
credit card revenue at many washes, it makes it pretty easy to verify income with those statements