1. I'm a stay-at-home mom because of what the Bible teaches, and the results I've seen from obedience
In Titus 2:3-5, the Bible says, "Older women likewise are to be reverent in their behavior, not malicious gossips nor enslaved to much wine, teaching what is good, so that they may encourage the young women to love their husbands, to love their children, to be sensible, pure, workers at home, kind, being subject to their own husbands, so that the word of God will not be dishonored."
Where does the Bible talk about women having careers, or supporting their families? Proverbs 31 does talk about what a virtuous woman would do, and it encompasses a variety of things. All of those things are "support" for her family, but they are home-centered: she is caring for her household. She isn't off working in a factory or waitressing at a restaurant while she pays someone else to care for her children. She isn't sitting in an office while her precious children are being educated at the local public (or even Christian) school.
Instead, she is home. She is working at home... preparing food, seeing that everyone is clothed, working in her field, making things and just generally being productive. Her husband and children call her "blessed", and she causes her husband to be respected and honored by others.
I won't take the time to go into detail about everything the Bible says about a woman's responsibilities, or everything that a good wife does for her family and household. I simply want to say that the Bible portrays a woman as a wife and mother, caring for her husband and children, and NOT as a successful career woman who is a wife and a mom in her spare time.
"Success" as our culture defines it is so different from the "success" that the Bible teaches. The world doesn't really care if your children don't love God; that's "okay" as long as you live in a nice house, wear the latest styles, and drive a nice vehicle. I've seen those families... the ones where the children go through all the "normal" stages of life, where a few of the daughters get pregnant out of wedlock, where a few of the sons use drugs, and where almost all of them grow up to enter unhappy marriages, trying to juggle careers and maybe one or two children, if they feel they have the "time" to plan a child in there.
On the other hand, I have witnessed close families, with multiple children, where the siblings actually get along and love to be together. Families where the children have learned real skills and exceptional knowledge because they had a personal "teacher", their mom, spending time educating them, long before the "normal" children even got sent to pre-school. Families where the daughters and sons actually remained pure for their wedding day.
I'm not saying that just because a family has a stay-at-home mom, their life will be perfect, or their children will be "perfect". But I have seen how obedience to God's word produces good fruit.
2. Having the wife/mom stay home actually saves money
I was raised in a home where my mother didn't have an outside job. Oh, she had plenty of "jobs". In fact, I think her "job" list is never-ending! Gardening, caring for her children, cooking, cleaning, homeschooling... the list goes on, and what would have to happen if she had an outside job? Well, the children would be in public school. The cooking and cleaning would have to either not get done, or largely be taken over by someone else, whether it meant going out to eat or buying quick frozen dinners, and hiring a maid to clean the house.
But wait, because all of those things cost extra money.
For example, simple cooking can be learned by even grade-schoolers (so a mom has no excuse for "not knowing" how to cook*!), and can save so much money on food. A wife who has the time to pack her husband a lunch for at work, or make dinner every night for the family, will not only be feeding her family healthier things, but saving a lot of money. Eating out even just a few times a month can easily increase your food budget by 20%. If you don't believe me, just keep track of how much you pay for each meal every time you eat out, and add it up at the end of the month. ;)
If you have children, you must calculate the cost of daycare. No one will ever care for and love your children like you would yourself, even if you think you have found the most loving babysitter for your children. And here are so many women, paying money for inferior care for their children rather than staying home to be a mom.
If you're sending your little baby off to daycare, you're either going to have to express breastmilk for them, or do as most working moms do, and feed them formula. Besides the great benefits of breastfeeding that you would be missing, have you ever priced formula? Breastmilk is free, along with being better for the baby AND the mom. Most daycares wouldn't allow cloth diapers, so you can also automatically add the cost of disposable diapers, along with extra trips to the doctor because of all the germs that get passed around from child to child.
Public school is "free", but you should at least know the statistics for how many 14-year-olds in public school aren't virgins anymore, or how many 16-year-olds have smoked marijuana. Homeschooling can produce remarkable academic results**, surpassing public schools.
With a two-income home, you usually need to have two vehicles, so add up the price of an extra vehicle, the extra insurance, and all the extra gas from running kids to daycare and going to work.
And since you will be adding to your husband's income, you'll both get to enjoy paying higher taxes. One-income homes often pay a lower percentage of the income to taxes, so your husband might bring home more when you stay at home than he does when you work outside the home!
Besides all these bigger things, there are so many things a stay-at-home wife and mom can do to be frugal. Simple mending, cooking from scratch, watching for sales at the grocery store, packing lunches, giving her children haircuts, going to thrift stores or garage sales instead of paying regular price for everything... the list goes on, but this isn't meant to be an article all about thriftiness. ;)
So, add up the costs of working outside the home, and you may find that you're working 40+ hours each week and earning just a dollar or two an hour by doing so. I know of a woman who admitted that she was actually losing money by working at her job, but she just didn't want to spend all day at home with her family.
3. Having the wife/mom stay at home is better for the family
A home where the wife/mother stays home all day can be much more peaceful and orderly. The mom spends all day with her children, teaching them how to run a household and homeschooling them. They do things, fun and educational, all day. The parents know what influences their children are around. They control what their children see and hear. When something sinful is noticed, the parent is there to say, "Do you see that? That is wicked. YHWH says not to do that. We want to obey YHWH, don't we?" :)
Parents who homeschool aren't necessarily trying to shield their children from sin, but rather to equip and prepare their children to respond to sin. A 5-year-old isn't usually ready to be thrust into a group of other 5-year-olds who already have dirty mouths and rebellious ways, and be expected to not conform, especially when they spend every weekday with these same children. Home educations allows for a broad education where the parent is learning right beside the child.***
A wife who stays at home has time to make nutritious meals. She has time to serve her family. She's there when her children need her. She knows that a healthy marriage and an orderly home are worth far more than expensive furniture, entertainment, or luxuries.
But......... How can you afford to stay at home when your husband only makes ____??
Reduce your expenses. We all pay money for things that we don't NEED. Realise that you CAN live on less. Realise that investing in children is for eternity; investing in "things" is worthless. As a wife, be willing to go without for the sake of your family. If there is extra "spending money", let your husband enjoy it. Stop trying to make more money, and start trying to spend less.
Some people who think they must have two incomes to survive might be surprised if they learned that other families live comfortably on less than half of their budget. Start budgeting, and start figuring ways to reduce your spending.
A friend of mine told me that her husband says, "If we can't live on my income, then we're spending too much." What a great outlook, and so vastly different from what the world tells us.
As for me personally, I just couldn't afford NOT to stay home.
*I am NOT saying that everyone must LOVE to cook. I don't always LOVE to cook. :D But what I am saying is that when a woman dislikes cooking and would rather work outside the home so her family can go out to eat or buy prepared foods from the store, she is being selfish. Being a good mom often requires sacrificing our "free time" and our own desires for the good of the family.
**I am NOT saying that "all homeschoolers are smart, all public schoolers are dumb". But homeschooling cannot be dismissed on a purely academic level.
*** We love to tease my mom about having to take Algebra classes for so many years, since she has taught it to us all. (She currently has two years of Algebra II left, and one year of Algebra I). ;)