I really need money...any tips on how to make it?!?

I'm a 17 year old student and starting my second year of college... I have tried all summer to get a job, but keep getting rejected, or don't hear back from anywhere. Now term is starting again, I probably wouldn't even have time for a job as my cw load gets very very heavy. ( I usually have to spend almost every evening on it) But I really desperately need money, not just for myself, but so I can help out with my parents a bit. We have always been a little poor and I'd like to give something back to them. Is there any other way I can make money? I've considered ebay, but find it a little confusing, and not sure how likely things are to sell ? and how much paypal deducts? (I know ebay take 10%) any other random tips are welcome :D :D xx