Daycare, for example, is expensive. When you're figuring out if someone can stay at home with the kids, you have to remember that certain costs go away.

Being a stay at home mom also can mean that you eat at home a lot more. It might not mean that, but if you care to cook much at all, you'll have more time for it when you aren't working away from home. Even on days that the kids have really busy schedules you can always use the crockpot to get things going early. Trust me, the crockpot is your friend. That goes double if the children are young and clingy.

Especially with gas prices going the way they are, you can cut a lot of money out of the budget simply due to driving less. What you save will depend on how far you've been having to go to work, or if you've been able to use public transportation.

The clothing budget for the stay at home mom probably also drops. There's less worry about dressing right for your job, and you will probably wear far fewer dry clean only outfits.

There will also be a difference in your taxes. A lower income does mean lower taxes. This is a hard one to calculate, but it's worth remembering if things appear to be borderline.

Some saving money skills can take time to master if you haven't been practicing already. Clipping coupons, for example, can theoretically save you money, but many people spend even more because they aren't being careful about buying things they don't need. No matter how good the deal is, if you aren't going to use it, it's not a good deal.

Your savings can also be eaten up by the desire to put your kids into more activities. Many of these add up pretty quickly. They also add a lot of running around in the car. There's a balance between putting the kids into activities they'll enjoy and what is reasonable on your budget. You have to find the right one for your family.

And don't forget there's a huge value to unstructured play for children. Remembering this can keep you from running around to an excessive number of activities.

When in doubt about whether or not you can afford to stay at home, consider testing the situation. Try living on just one income, and saving as much as possible of the second.