I was talking with a guy yesterday who's owned a car wash since 1989. All automatic, no personnel, all cash or credit/debit. He says he used to make ~45 % gross profit, but now it's a lot less. Utilities keep going up (as does everything else), but customer pricing increments are minimum 25c per raise, which is really noticeable. Put the user price up 25c and you suddenly get a lot fewer car washes. I didn't get his GP figure now, but sounds like it's much less; he says he wouldn't buy one now. He keeps this because he owns it outright.
Not saying it wouldn't work elsewhere, but just run your numbers and figure in all utilities and maintenance costs; also commercial loan costs which are significantly higher than getting a mortgage. Also market conditions....both micro and macro. Where's the wash, what sort of business does it do (go stalk it) and what are the wider trends for the general populace washing their cars? eg. in Australia, all those car washes recycle the water...