If you only want two cars a month then I wouldn't bother advertising with flyers. Two cars a month isn't part time or even part part time. Don't advertise unless you are prepared to handle the volume of customers it may generate. Just start out with word of mouth around the neighborhood, work, and family.
I would also consider adjusting your price a bit. $50 bucks for two or three hours worth of work doesn't seem like it is worth getting out of bed for. Detailers don't make that kind of money unless you are working for someone else. Self employed detailers charge upwards of $30 - $50 per hour. I'd evaluate how much time a car will take you and how much you want to earn doing it. If you undercut every other car was and detail shop in the area, then people will wonder why you are so cheap. Some might assume it is because you don't use the same quality products or tools. It's something to think about...
As Greg said, do some searching on this. I posted something on making money detailing from my site awhile ago. It might be helpful.