How old do you have to be to start earning money from your blog?

Me and my friends share this blog and we update it weekly. We have had it for a couple of months now and we would like to start earing money for it. I have heard about AdSense and things like that but is their a minimum age that you can get money from your blog? Here's our blog : www.fab.webeden.co.uk this is a fashion and beauty blog :)