Your age will limit the amount of things you can do since making money online often time requires you to have certain documents to prove your age. If I was you I would make your own website or learn about online marketing or web design. When your old enough you will already have the experience to make a website for money. I made my first when i was around 16 that was 14 years ago.

You could try an arcade website and sell ad space or use adwords, a blog, or find a game where you can sell stuff like gold.. a good example would be Diablo 3.

You Can Sell Unneeded Things On EBay

lol i was gona say get a job but then i realized u were 13

ummm you can mow neighbors lawns or just helping ur neighbors do work in general

Housesitting

dogsitting

babysitting

mowing lawns

Become the new justin bieber

shakin' dat a$$

Hey, I've got a paper run job and I don't want...

Lemonade Stands

Surveys

Garage Sales

Or any of those

I'm 13 years old In NZ and don't want to take money of my parents