Insure yourselves, too, especially if you're planning on a family. Healthy, nonsmoking 31-year-olds seeking $500,000 in coverage might pay between $224 and $339 apiece in annual premiums for 10- or 20-year level term policies, according to Insure.com.

About that family: The U.S. Department of Agriculture says it costs more than $200,000 to raise a child. You might be able to do it for less, depending on where you live. Get a ballpark figure with this calculator.

Planning to go back to work? Child care averages from $4,650 a year in Mississippi to $18,200 in Washington, D.C. But one of you staying home might result in "more debt, less in retirement savings, atrophying job skills and greater vulnerability to economic setbacks," says MSN Money columnist Liz Weston, with lower lifetime earnings and retirement benefits thrown in for good measure.

New ways of spending

In your single days, you might have been willing to nuke a frozen dinner or just eat cereal a couple of nights a week. Or maybe you were a raw vegan who spent hours preparing your food. Now you have to consider someone else's tastes and needs.

"More likely than not, there will be more takeout dinners, more roasted chickens picked up on the way home from work and more restaurant meals," Masini says.

Maybe the two of you could take a class (cost: not cheap) or teach yourselves from books and online cooking sites. It could become a new hobby, with his-and-hers "Kiss the Cook" aprons.

And speaking of hobbies: Are you startled by the costs surrounding your partner's love for golf, quilting, DVDs or role-playing games?

Or what about treats? She likes craft beer and massage; he likes graphic novels and sci-fi conventions. Each secretly resents the amount the other spends on "that stuff."

When does an indulgence become a deal breaker? Only you can answer that. Maybe you're willing to let him/her spend a lot because you think love is worth it.

Within reason, it might be. But I'd like to suggest that a trip to a financial planner makes a very nice date.

Donna Freedman is a freelance writer in Seattle. You can find more of her writing on MSN Money's Frugal Cool blog and at Surviving and Thriving (motto: "Life is short. But it's also wide.").