What age to Start ???

Hey guy's hopefully you can help me out with this
:)
Ive only been surfing for a little while know but the last 2 sessions i have gone out my sister has brought her son with her to watch !!! he is 5 and really wanted to have a go !!!
He is an ok swimmer for a 5 year old, but was just wondering what age someone could actually start learning to surf and if so where is the best place to buy kiddie boards and which sizes would be best ???
He is already wanting to come with me everytime i see him so i guess he has the BUG !!! even tho he hasnt been in hahahaha
Let me know what ya think guy's

Ive only been surfing for a little while know but the last 2 sessions i have gone out my sister has brought her son with her to watch !!! he is 5 and really wanted to have a go !!!
He is an ok swimmer for a 5 year old, but was just wondering what age someone could actually start learning to surf and if so where is the best place to buy kiddie boards and which sizes would be best ???
He is already wanting to come with me everytime i see him so i guess he has the BUG !!! even tho he hasnt been in hahahaha

Let me know what ya think guy's