Perhaps an equally informative question would be “How young is too young?”. For me, having children in my 20s would’ve been a disaster - financially, physically, and particularly mentally, I was a wreck. And I didn’t have a support network (with twins, that’s a necessity!).
But if you can pass the “not too young” test, I’d say go for it ASAP. Having children is the greatest joy I’ve known - and I’m a joyful person! It’s a LOT of work, but soooo rewarding.