(MONEY Magazine) – By most standards, Stephanie Brandt and Peter Cornais are a step ahead of the game. Both just 23, Stephanie and Peter are in love and plan to marry one day. They have good jobs, he as a civil engineer with an environmental cleanup company; she as an administrator with a different company in the same business. They earn good salaries--a combined $87,500 a year. And with their recent purchase of a good-size house in a hot Tallahassee neighborhood, they may be in position to ride a historic real estate wave that most of their contemporaries will miss.

So why are they living paycheck to paycheck, bickering about money and, in Stephanie's words, "freaking out" about their finances?

The answer has a lot to do with the sometimes infuriating process of becoming a couple. Peter and Stephanie may be better off financially than many others their age, but they haven't quite figured out how to make money decisions together. They're going through what a lot of couples go through during the first year of marriage. Only they're not married.

Last December, around the time Stephanie and Peter graduated from Florida State University, where they met, they told her dad of their plans to get married--eventually. (In classic fashion, Stephanie is in a bigger hurry on this score than Peter is. They still don't have a date.) Stephanie's father gave his blessing and a pre-engagement gift of $15,000 to be used either to pay for a wedding or to buy a home. Figuring that blowing so much on a wedding would be a waste, they went for the house.

It wasn't just any house. This past January, the couple closed on a recently built $299,000 three-bedroom colonial in an upscale planned community called Southwood. Peter tapped his life savings of $8,000 to pay the closing costs. Never mind that the house is too big for their needs and that they feel out of place among all the families there. "We're in our twenties and we have a pit bull," Stephanie says. "We get a lot of looks." They take that in stride because the Tallahassee real estate market, like so many others these days, is hot--Stephanie says their house's previous owner made 20% on it, having held it for only one year. Rather than making the house their home, the couple hope to sell it in three to five years and relocate close to a beach (they're avid surfers). "We've got a pretty strong feeling that we will make some profit," Stephanie says.

In the meantime, though, they're struggling with the sudden jump in their cost of living. The couple's monthly housing expenses, including mortgage payments, property taxes and hurricane insurance, now run $2,300 a month vs. the $850 in rent they were used to paying. That's over 40% of their take-home pay, leaving them about $3,000 a month to cover food, utilities, discretionary spending and savings.

While that should be ample for a young, childless couple living in Tallahassee, it's not for Stephanie and Peter. Where does all their money go? They aren't sure. Yes, they acknowledge, Peter bought some power tools recently for his woodworking projects. Sure, they bought a new washer and dryer. Of course, they sometimes enjoy dinners out. And then there's that $6,000 student loan that Stephanie is still paying back. But the expenditures the couple can account for don't seem to justify how financially strapped they feel.

Yet when Stephanie and Peter try to get serious about keeping track of their bills, they often find themselves in arguments, some petty, some serious. For instance, Stephanie was recently ticked off that Peter wanted her to use her credit card to buy a new iron, which she'd use to press his shirts. She also gripes that she can't get him to budget and that he still has not signed up for a 401(k) at work. For his part, Peter isn't happy about her plan to go out on her own as a massage therapist. Because he makes more money, he currently covers 60% of the couple's shared expenses, and he worries that the change will shift even more of the financial responsibilities his way.

Meanwhile, the house has barely any furniture, the backyard needs a new fence and the couple have little in the way of savings. They're yearning to get on track financially. Yet they're equally determined to hang on to their big house.

The financial planners MONEY contacted say Stephanie and Peter will be able to get their expenses down by refinancing from their 5.75% 30-year fixed-rate mortgage to a 5/1 adjustable. (They all advised against an interest-only mortgage: too risky.) There would be little risk, notes Mari Adam, a Boca Raton planner, since they plan to sell the house before the rate would adjust. But because fixed-rate mortgages are currently so low, the savings would be small--only about $200 a month at today's rates. And they'd still have to pay $1,800 or so in refinancing fees, so it would be about nine months before they'd start to feel a benefit.

» FACE THE HARD DECISION Which is partly why the planners feel that keeping the house isn't worth the problems it's causing. If this were the couple's dream house, and they hoped to raise a family there, perhaps they could justify stretching themselves financially to keep it. As it is, Stephanie and Peter are putting their financial future and maybe the health of their relationship on the line for what is a speculative investment. (They paid only 5% of the purchase price as a down payment, so even a small decline in prices could put the investment in the red.)

Ruth Hayden, a St. Paul planner who specializes in counseling couples, says Stephanie and Peter have to make a tough choice: Postpone their long-term goals while they hope the house appreciates, or get on with their lives. To her, it's no contest: "They should be thinking about creating a home, not an investment."

» DECIDE ON COMMON GOALS A part of Peter and Stephanie's problem, they admit, comes from tension about the uncertainty in their relationship. They're going to get married but they haven't set a date. They don't even consider themselves officially engaged yet. But they have all the financial headaches of a married couple without the public better-or-worse declaration that comes with saying "I do." Stephanie and Peter first need to clear the air, talk through their emotional and financial goals, and then together set up a savings and budgeting plan. Hayden suggests that they open a joint account for shared expenses, which will enable them to track all their outlays and identify areas where they can economize. Assuming these moves free up income, they should start setting aside cash--maybe $300 a month--for emergencies. And Peter should start contributing to his 401(k) to take advantage of his company's match.

» PUT IT IN WRITING Hayden also says that if they aren't going to get married soon, the couple should formalize their financial relationship with a domestic partnership agreement. In particular, they need a written, notarized agreement about how to divide the proceeds from the sale of the house. The goal, Hayden says, is to keep emotional tensions from manifesting themselves in arguments about, say, who should pay for the iron.