To make it simple and quick ? this will make you a good $150 per day.
Jst invest on a extention cord,long water hose with fittings,vaccum cleaner, 3 sheets of sand paper 2000, soap, a few rags, reduceble armor all, big towells --rubbing counpound (to remove 3000 marks), and start knocking on your neighbor's doors.
Be like. Hello, I'm ur neighbor ... I am raising funds to help my parents, and I am offering to wash your car for $35.00 inside and outside. You can watch me while I do it, so you can tell me how I did. Also, I brough these 3000 sheets to remove all light scraches.
And Smile !
I'm telling you bro ... if you sound inosent enough you will break their heart and you make your money ... if they bargain, go down to $25 minimum.. Spend a good 30 Minutes, and work your ass off to go to the next one..
IF you go to staples, and order those very cheap business cards they have, it will give you a way bigger chance.
Good Luck bro
Note that you will need to borrow your neighbors water and power, thats why you bought a hose and extention cord..
Buying those thigns to make their car smell good will help too.
You wash 5 cars you made $150 dollars ... I love washing cars lol I'd do it again if I needed to, except I have winter here so it wont be a all year job