There was a DIY in a very upscale area near me. They offered self serve or they would do the washing for $5 more. Now, they didn't offer any grooming, nail clipping etc. I never saw anyone in there, and the space it was in you could see everything. It didn't last long.
Self service around here does well as an add on. The feed store down the street has two tubs. We used to have our shop in that store and could hear everytime someone was using them, and on the weekends that was alot! Mostly summer time too.
Now starting up mobile I am offering self serve as an option. I don't know how many people will want to use it for that BUT I am not relying on it for income. I know what I will have to charge for it to be profitable, but when I wrote my business plan I didn't include any money I was plannin on making from that. I put it separately, and that way I know how much it costs to run the rig, how much I would have to charge, and if it doesn't take off, my business isn't really reliant on it. I just saw so many people walking sopping wet dogs out of the DIY because they were charged per every 30 minutes and no one wanted to pay for more than 30 minutes. Then they'd be taking a dripping wet dog into their car. This way, if they don't want to pay for more tha an hour, they don't have to put a wet dog in their car or worry about a long cold car ride hom etc. Plus I am using the self service option as a way to try to set myself apart.
Once I am up and running I'll let everyone know how it's going!
What a caterpillar considers the end of his world, we call a butterfly.