This is a terrible idea.
Age =/= maturity. I'd say future parents would have to get a parenthood course, and then tests about various subjects: caring for the infant, answering a children's questions, understanding a child's psyche, how to raise the child's self-esteem and be a stimulator in their lives, general knowledge to pass on, financial budgeting with a child, time monitoring with a child, how to let your child develop their own identity, how to not impair your child curiosity while still keeping them away from danger, etc.
There's too much parents raising bratty, snotty nosed potty mouthed kids around here. They don't even care for their children. They walk literally feets before them. I could totally kidnap one, have a nice walk, get them some icecream and bring them back to their parents an hour later, and the parents would barely notice. Children are not accessories or pets.
You can manage being poor and have children: breast feeding for as long as the child wants (not as long as society prescribes as socially acceptable), washable diapers, limiting toys (replacing them with human, parental interactions), transporting the baby with a baby scarf instead of a stroller, buying used clothing (they'll grow out of them soon enough anyways), etc.
You cannot manage raising a child while being stupid. Well, you can, but you'll raise some bigoted, bully asshole that won't bring anything good to the society.
Also, if you only have chidlren by age 30, most children would be born with major malformations or disabilities. That's not a life you want for your children... Also, there are 14 years old that'd probably be more concious of the nature of life than some childish 35 years old that had it easy all their life... :/ Think about it.
I do agree male should be fitted with contraception at birth, tho. It wouldn't be worse than child circumcision :/
There's something already invented in India that'd be perfect: it's some kind of material they inject in the appropriate canals and they can later dissolve them with a very simple injection. I wonder why it's not here yet...
Anyway, that's my opinion.
On another topic, I also find it terrible that children can't vote. If you explain them what's going on, they can judge fairly (with the information they have). It's unfair that the citizens of the future's voices are impaired...If we would take time to explain, leave them participate.. We wouldn't have such a disinteressed youth. I mean, ask any 12 years old about the elections, they'll probably say "I don't know" or "I don't give a shit".