Some of this might be common sense stuff, but I thought I'd write it out anyways:
1) Get a financial history of the wash. Don't buy it without. If he's not willing to show you what the wash is bringing in, then he has overpriced the business and/or it's not making any money. He should be more than happy to show you the income to facilitate the deal. (It sounds like you have this already, but it is the most important)
2) Talk to a business lawyer that can write up a rock solid purchase agreement.
3) Try to negotiate atleast a month of
training from the previous owner in your purchase agreement. This will save you a ton of time and trouble when problems arise.
4) Talk to an accountant on how to breakdown the purchase. X amount of dollars for the equipment, X amount of dollars for the building/land, X amount of dollars for goodwill. This is invaluable come tax time.
5) When looking over the wash, check for any major expenses that may lie ahead. (Is the parking lot in good shape, is the floor heat working properly, does the bay equipment need to be updated, etc)
6) When going to the bank for financing: Go to every bank in your area. I went to 10 or so banks when trying to get my financing. I got really good offers from some, terrible offers from others, and a "not right now" from another. Come up with a financial spreadsheet that proves that you will be able to make your payments even in the worst of months, this will help the commercial lender and it shows you are prepared.
7) Finally, ask yourself if you are willing to commit to the 7 days a week schedule that a car wash requires. Days of continuous rain are your only days off. Ensure you can physically and mentally handle this schedule. If you plan on having employees, ensure that you can put in a system that prevents employee theft or find someone you can trust that will be reliable.
There's more, but that's the jist of it. Good luck!
