I waited and ended up with 60K+ in fertility treatments. Tick tock, tick tock ...you might be someone who has no difficulty or incredible difficulty. Our fertility decreases as we age, that's just a biological fact.
If kids are very important to you, and you want a bunch of them, consider that you'll have more work-around options and more chance of success if you're younger.
I was 36 when I "decided" to have a baby, so older than you (by far). There's no definite number, though. Everyone encouraged me to take my time and assured me that I should have no difficulty ...even my ob/gyn.
Weigh everything, but keep in mind that there's rarely a good time to have kids.