I would think the best time to have a child is when you can support all that child's needs. I think you would need enough income for the two or three of you. Are you going to be a single Mom? Also there are the emotional needs of the child, and these out weigh your needs, as the child does come first.
I think if you have to ask this question, you are too young, we did not have our first child till we where in our 20's and I think I was still emotionally to young.
There is no "minimum age" to have a baby. Even if you got pregnant at 12, you would still be allowed to keep your baby - nobody can take that away unless you prove yourself an unfit parent. However, there may be some serious legal repercussions for the father of the baby if certain laws are broken.