I agree with Cheryl
I have a yearling (well will be in two months) & it's HARD work
I get up at seven everyday to go out & do morning training with him for basic stuff like: putting on the halter,leading around,maybe some free lunging,do some parelli games
So unless your super committed to getting up & working your butt off I wouldnt get a yearling or anything younger.
Many people make the mistake thinking it'll be a great thing to get a foal & raise it but most of the time people who aren't experienced end up getting mad & upset easly at the foal when in truth the foal isnt really doing anything wrong
So I agree with Cheryl, it depends on experience