Well here's my suggestion. do something good for your town and become a Volunteer Firefighter. Most fire stations have a wash bay and the members are free to wash theirs cars anytime you want. Mine charges $1. If no one is waiting I can stay in there all day or night. It's warm in the winter. Not only do you have a clean car you are doing something worth while for the community. I've belonged for over 30 years even though I don't fight fires anymore.
Very good suggestion, though it unfortunately doesn't work for everyone. I used to be one in my town, but both the politics that overran the dept, and the fact that I moved to the outskirts between two districts and changed jobs, just left me unable to continue. But while I was there, I did have the ability to use empty bays whenever, plus we had the pool table upstairs. That said though, we were limited to personal cars (and immediate family, as long as we were the ones washing). Ours wouldn't approve if I was using it for a for-profit job. Different places obviously would have different rules.