The poor never seem to worry about not having enough money to raise a family of four or six or eight.
And here's another piece of the puzzle: according to Dr. Brian Ray, HSLDA-related researcher, referencing U.S. Labor Dept statistics, homeschooling families are to be found at every income level. Keep in mind that homeschooling couples generally have one working full-time, one homeschooling full-time. They have one income, maybe one-and-a-half if the teaching spouse also, say, works at home part time.
But somehow, some households manage living on one income at every income level.
The homeschooling decision seems to be determined, not by what their income is, but by what their values are.
I'm thinking the same goes for the decision to have kids in the first place.