Tass, I am in the same boat as you. I consider myself a *mobile* detailer but Im not truly *mobile*. I go to businesses and houses that can supply me with water and elec. outside. This didn`t go over as well as I planned since not a lot of business buildings have that, but it has gone ok. I would really prefer to go to people`s houses and work there in their driveway. No this doesn`t give me HUGE exposure but their neighbors will see it and the client`s will give referrals. I usually do a basic wash, quick spray wax, wheels, vacuum, dash and windows on a vehicle for people. $30 cars/ $35 trucks/ 45 small SUV`s/ $60 large SUV`s. Thats cheap for some people but I`m not in a very prosperous college town. Most people are very pleased with these prices and my work and usually throw in some extra$$ as a tip. When they`re pleased they give referrals. I leave a brochure in their car with a personalized note. The brochure explains what I did to their car and what I can also do in the future. I like to explain that when I can but sometimes they just dont have time to go out and see their car. They usually pass this brochure or my original one along to someone else. I`ve never seen my brochure back in the car the next time, so I hope they`re giving it out and not chuckin it.
Granted for most people the basic is fine. They want no more than that. I do feel under appreciated when I do that because anyone can WASH a car. But the money is there, fast and simple. $45 for doing an Xterra in an hour and 40 minutes isn`t bad.
I think I`m rambling a bit so sorry. I`m trying to kill time inbetween my classes. I`m like you, Im trying to balance work and school together. Even though my course load isn`t heavy Acct. and other classes take a lotta outside work.
Try and present yourself really well. You have to find the line between explaining what you can do and arrogance. You sound really knowledgeable about products so just use that. Try and ASK people what they want done while explaining it. I tell them what my basic includes but then I say I can apply a better longer lasting wax for $15 more. Or I can also clean up your engine abit for $10 more. Since your paint is black it easily shows swirls, I can fix those for... Just try and find your niche at advertising YOUR skills. Of course Im a marketing major so this comes semi easy to me.
One thing I did that has really helped me on getting some business at homes is a press release. I put one out in my local paper explaining what I do and where I can work. I try and make it explanatory and sell myself at the same time, without sounding like an advertisement. PM me and I`ll show you the article the paper ran. They edited it slightly from my submission but it turned out good.
Sorry the post was so long. Just realize that it can be done even at a young age but you have to find what works for YOU. Then you can branch out later if you need to. Im considering going *truly mobile* but can`t just yet b/c of $$.
Hope this helped some.

-Josh