Can you afford to stay home after the birth of your child? In an attempt to answer this question, many folks use too simple an equation -- typically looking at a rundown of major bills, adding the cost of child care, and then comparing the expenses to their income. The trouble with this calculation is that it fails to do a couple of important things, such as (1) factoring in the true cost of working and (2) acknowledging many of the "hidden" financial benefits of employment.

That simple calculation also assumes that bills are an accurate gauge for how people spend all of their money. In reality, a lot of money drains out of the family coffers for incidental expenses (anything at Target), ATM withdrawals (huge chunks of cash unaccounted for), and daily dribbles (almost any habit, like Starbucks). Getting an accurate picture of where your money goes is an important step in determining if you'll actually be able to live off of one salary.

Step 1. Figure out where all of your money goes.

  • Look at your fixed bills
  • Keep track of all of your spending (the Fool's budgeting calculators may give you a hand)
  • Identify all of the ways in which you could cut back
  • Add back in a realistic budget for essential baby items (clothes, diapers, etc.)

Need more encouragement to budget? Try:

Step 2. Figure out what your two incomes will boil down to, after expenses.

At first blush, it may seem like income from a job is pure profit for your family. In reality, jobs can spawn expenses, as well as boost you into a higher tax bracket -- both of which can take a big bite out of your take-home pay. Be sure to consider these costs of having a job:

  • Child care
  • Dry cleaning
  • Professional wardrobe
  • Commuting costs (gas, fare tickets, wear and tear on your vehicle)
  • Higher car insurance costs (depending on the length of your daily drive)
  • Parking
  • Eating out or buying convenience foods that boost your bill
  • Household services (housekeeping, lawn maintenance, or other services for your home that you no longer have time to perform)
  • Daily Starbucks habit
  • Buying your colleague's daughter's wrapping paper and Girl Scout cookies
  • The effect on your tax bracket
  • Cell phone, pager, or Treo costs

Your picture would be incomplete, however, if you just stopped there. Be sure to look at all of the financial perks of outside employment, beyond the increased income. You may be surprised by how many benefits exist beyond your paycheck.

  • Dependent care benefit programs and 401(k) matching from your employer that can add significantly to your bottom line over the long haul
  • Access to training and educational opportunities that boost your value as an employee
  • Keeping your professional skills current
  • An alternate health-care plan that may offer better benefits than that of your spouse
  • Insurance benefits from your employer (life insurance, short-term care, or disability insurance)
  • Pension benefits
  • Other possible perks, like subsidized gym memberships

Your considerations won't be purely financial, of course. You'll have to factor in your (and your spouse's) opinions about parenting, as well as gut feelings. But having a handle on whether or not you can make it work from a financial standpoint gets you that much closer to making the optimal decision for your family.

This article was first published on Sept. 8, 2007. It has been updated.

Fool contributor Elizabeth Brokamp is a licensed professional counselor who talks money with her honey, Robert Brokamp, editor of Rule Your Retirement. The Fool has a disclosure policy.