BOY......are you in for a ride!! I agree with the previous posts in regard to obtaining an account without having all the proper knowledge or experience. That said, here's my input.
We use to (USE TO) wash roughly 3,000 cars weekly. Our method was cold water wash (1 sprayer) with 2 chamois guys behind. No chems! (Unless I'm missing something, don't know why you'd use chems unless what you're offering is a soap, rinse & dry. In that case, if you're not charging $3 - $4 per car, you're gonna' loose your A*!@#., and lucky if you could do 100 cars per day.)
We had to start at sunrise so we could be "mostly" done before the dealerships opened, and avoid the high heat in the afternoon. Even then, on a 300 - 500 car lot, we'd still be spraying during operating hours. Wandering customers will slow you way down. Every car dealer wanted washing no sooner than wednesdays, and most want Friday so the cars are "standing tall" for the weekend. This limits any other work you can schedule toward the weeks end. THEN...it looks like rain tomorrow!! The dealers never understood that rain doesn't clean the cars. We'd literrally be calling the crews at 10 - 11 pm, or 4 - 5 am to let them know if we were working that day. If we had to call off the wash, we'd have to hope there was something else to do to fill the void.
Spot free? An RO system (reverse osmosis) is the only TRUE way for spotless without chamoising. Extremely expensive option and not feasible to carry that much water for a large lot. Yes, you could do this with a large cube van with a mounted RO system, but maneauvering around a lot gets difficult. I tried all sorts of spot free rinse agents, soft water, etc. when I did winter washes - nothing really worked to our satisfaction.
Labor......A headache in any business, but......As I stated we had 3 man crews. If one guy doesn't show up, nobody works. I chamois guy can not keep up to a sprayer. Better have young, healthy people. That much bending, reaching, wiping, etc. gets REALLY tiring.
Insurance.....If you don't have it already, lock up your equipment and find another hobby please! Hoses get dragged over the fender of a car and leave scratches. OOPS - $500.00 Your spray pressure just lifted off loose paint on a used car (used cars demand greater attention from the sprayer because of loose paint, trim parts, etc.). OOPS - $500.00 Not to mention employee injuries that can occur and the fact that you have people walking around the lot between cars and suddenly pop out behind a row directly into your spray.
Maintenance......this work is hell on machine wear. There were times we'd be running 500+ foot of hose (between supply & pressure) which is not good for the pump. We'd run the machine non-stop for 1 - 2 hours at a time. Cars running over the hose, and on and on and on.
Our average price was $1.35 per car, averaging 55 cars per hour. We paid the crews per car - $.20 - $.25 per car, per crew member. At $.25 for instance, our gross profit was $.60 per car, which really wasn't bad but didn't outweigh the other issues.
The moral of this story: We completely cut out our car wash service. We maintained sales the following year by focusing on more profitable business and reduced our payroll by 85%!!! We eliminated a ton of liability and cost for maintenance etc. Now we're in control of our schedule instead of the dealerships.
Yes....you can make money doing cars. You can make money at ANYTHING if you have enough business sense and there's a market.
Hope all this info. helps. Good Luck!