Waited until I had a house, built my business and found the right partner.
I was 44 when I had a son.
He's now 16 and the girl is 12. It's good and we love it. But it's still an insane undertaking!
My advice: With your spouse, the #1 job is to be really good friends and communicate openly. This is the groundwork you build on.
There will be rough patches of many stripes. If you are besties, again it helps a lot.
NOTE: Financial security is great! We are lucky/smart enuff to have it, but if you are not friends it don't mean a thing. Side note: avoid consumer debt and be careful with heloc spending. Don't be stupid!
Keep working out/running. We are both fit, the wife and I. It helps in many ways, not the least of which is in the sack (dudes, be sure to be generous there, not greedy. Wait your turn. And you'll get all you want and need.)
Arrange your life / work to spend a lot of time with your kids. If you hang with your kids growing up, it's the best investment for everyone's future, including yours. Because you will know your kids and won't have regrets about missing their childhood.
As I'm a professional cartoonist, it has been frustrating to lose a lot of work time to parenting, but let me say I took my time to build the career and went into parenthood eyes wide open.
I'm out, don't want to be too big a bore! Cheers.