How old were your children when they started to get an allowance? How much did they receive?

DH and I are pretty set on the idea that there are certain jobs that you do simply because you are a member of the family, and there are other jobs that you might do to help out and earn a bit of pocket money, but we want to pick reasonable amounts. DS is 5 and seems interested in the whole idea, and it might be a good math experience (he's a little young, but a bit ahead in some math areas) for him ... but I have no clue as to what's appropriate.

Thanks for your input!