Where to start freelance work for a 13 year old?

Brad,

This question, or aspects of it, has come up on this site several times in the past. You might start by doing a search and reading those comments.

My understanding (and I'm not a lawyer) is that if you want to work in England and you are under 15 years old, you need some kind of working papers. In the US, it's 16. And you may not be old enough to set up the accounts necessary to receive payment.

While a casual job every now and then may not be worth the government's time, there may be legal ramifications for your parents or guardians if you don't check out local and international laws before setting up shop.