If you are not in a financial position to take care of children.
DON'T HAVE THEM.
Plain and simple.
I'm barely able to take care of myself. Not financially, but physically. I have issues maintaining my own health. I'm 24, and consequently have made the decision not to have kids. The money I make now is great for me, but wouldn't last at all for a family.
I have absolutely no sympathy for people who have kids when they know full well they are in no position to support them. Whether it be financially, emotionally or educationally. Or some combination of the three.
Don't want to be poor with kids to feed? Don't have them.