Look at Your Benefits
The finances are not the only piece of this puzzle. If you're leaving your job, and it provided health insurance for the family, you need to make sure that your spouse's job can provide comparable benefits. Likewise if you had a flexible spending account at work that saved your family a bundle by allowing you to pay for medical expenses and contact lenses with pretax dollars. And finally, don't forget to save for retirement. As the stay-at-home parent, you're presumably going to be giving up a 401(k) plan at work, and maybe even matching dollars from your employer. But you can still save in a tax-advantaged way through a Spousal IRA. "You can contribute $5,000 in 2009 as long as you file a joint tax return and the working spouse has earned income more than your contribute amount. You can invest that money any way you want," Goldstick says.
You are very likely going to want to go back to work one day, so keep your skills sharp by taking classes when you can, doing volunteer work in your field or staying on top of any changes to the industry. And don't forget to network. Just grabbing a coffee with a former colleague once a month or so will give you an in to reach out when you're ready to go back to work.