Guess, I think you could definitely make ends meet, depending on where you live and how self motivated you are. If you do good working by yourself, and enjoy working FOR yourself, might be something to look into.
Three cars a day (once you get going, obviously), 6 days a week, at, let's say an average of $100 per car (complete details average above $100, just exterior/interior, or odd jobs, may be below that, depending on area), $1800 a week, 7200 a month, or a nice $86,400 annual income. You might think I am looking on the bright side, but there are a lot of cars out there. You might make much, much more than that if you hire employees.
jazzyjack, great idea. I was planning on doing a bit of the same thing, handing out flyers to people with high end cars, or you never know, the soccer mom who might want the stains removed yearly. Also, sticking flyers under nice cars windshield wipers might be a good idea... not sure if you need to get permission for one car.
My few cents,
Josiah