7 year olds one can go forth into homelessness and  Arahantship can can be sustained, younger than that is unheard of.

> When I was seven    
> & newly gone forth,    
> having conquered with my power    
> the great powerful serpent,    
> I was fetching water for my preceptor    
> from the great lake, Anotatta,    
> when the Teacher saw me & said:
>
> "Look, Sariputta, at that one,    
> the young boy coming there,    
> carrying a pot of water,    
> well-centered within,    
> his practices — inspiring;    
> his bearing — admirable.    
> He's Anuruddha's novice,    
> mature in his powers,    
> made thoroughbred by a thoroughbred,    
> good by one who is good,    
> tamed by Anuruddha,    
> trained by one whose task    
> is done.
>
> He, having reached the highest peace    
> & realized the unshakable,    
> Sumana the novice    
> wants this:    
> 'Don't let anyone know me.'"

[Thag 6.10][1]


  [1]: https://www.accesstoinsight.org/tipitaka/kn/thag/thag.06.10.than.html