In the summer or now, Cut your parents/guardians grass? or maybe you do that out of good will, but ask your parents do they know anyone (elderly/disabled etc..) who cant cut there lawn and need someone to do it for them, You could sell your own stuff? if your parents let you!
now in my house im 14 aswell but i get paid to do the laundry i get 50c for the washer and 50c for the dryer and a dollar for folding each load and i pull out about 40dollars every two weeks also you could try washing cars and babysitting also i get paid for grades 20 dollars for every A but i have to pay for every D but it pulls out about 140 if you have 7 core clases and you get A's in all of them on top of the laundry so about 200 dollars every month or so :)
Become a computer consultant to all the people that use aol. Seniors often don't know anything about their computer. Charge them for your teaching them how to use a computer. You probably already know 100 times more about this!