MANAGING YOUR MONEY : PREPARE YOURSELF : Couples Crafting New Rules for Sharing : Forget ‘what’s mine is ours.’ That axiom has given way to divorce, the women’s movement and other factors that complicate domestic mergers.

Jeannette DeWyze and Steve Wolfe have been married 16 years. They have two children, a house in San Diego and two thriving careers. But every month, they sit down, add up their expenses and split them in half. They have never had a joint bank account.

Sarah Williams and Ron Thompson were married last year. They live in the condominium in Los Angeles that she bought before they married. She pays for their food and clothes. She put his name on her savings account. But his money goes into his business.

“Household expenses? Not my problem, baby,” mused Ron, an artist and general contractor who, like his wife, asked not to be identified by his real name. “This is a little early 1990s male chauvinism.”

There are few rules left governing how couples handle their assets. The women’s movement and the divorce rate have put an end to that. Some merge everything, a few merge nothing. And more and more, couples alight on some murky middle ground.

Usually, it happens haphazardly. They marry in their thirties with a modern-day dowry of bank accounts, investments and careers. Out of habit, they may start off keeping things separate. But they soon mingle them, all too often with little or no thought.

The consequences of their non-decisions can be dire. If the marriage ends, a spouse can lose more than his shirt. Yet financial planners and marriage counselors say they are struck by a common theme: how much money matters and how little it is discussed or understood.

“Money is critical in our marriages,” said Jean Flannigan, a psychotherapist in West Los Angeles. “I think it is the single most important symbol of the underlying issues. We project our psyche, or our soul, onto money.”

“People will share intimate information about their sex life with their best friend, but they won’t share their finances,” said Rose Greene, a financial planner in Santa Monica. “It is the most private subject, and it has the most amount of shame associated with it.”

There was a time when our hang-ups perhaps mattered less. Men made money and most women didn’t. Couples married young, without houses, investments, children from previous marriages. They pooled everything. After all, hadn’t they married for life?

But these days, most women work. Some earn more than their husbands or derive self-esteem from being self-supporting. Many couples marry later, in their thirties and forties, bringing wealth from an earlier life. And half of all marriages end in divorce.

Contemplating breakup, therefore, has become a necessary evil. Otherwise, ex-partners can find themselves fleeced--their hard-earned assets split 50-50 under community property laws or passed on, inadvertently, to a surviving spouse’s children from a previous marriage.

Under California’s community property system, money earned through either spouse’s work during the marriage becomes community property. If the marriage ends, those earnings must be served up for division under the terms of a divorce settlement.

But assets acquired by either spouse before the marriage can be held as separate property--not subject to division in a divorce--as long as an absolute separation is maintained and there is no intentional or inadvertent “commingling” of assets.

According to financial planners, more and more couples are keeping at least some property separate, especially in second marriages. Some do it because they have stopped believing that marriage is permanent; others do it to protect their children’s inheritance.

Many hold their house jointly, splitting the mortgage payments. Investments from before the marriage remain separate. They set up separate and joint bank accounts and credit cards. Only over time do they begin making joint investments and “merging.”

What is the best way?

Most financial planners insist it is impossible to generalize; any financial arrangement must be tailored to the couple in question. If there is one rule, they say, it’s that couples should talk about money in advance.

“A lot of it has to do not necessarily with just protecting the assets but protecting the egos,” said Alan Ungar, a certified financial planner in Calabasas. “It’s much less a financial planning decision than it is an emotional one.”

Rose Greene and Carol Rabaut have been lovers for 12 years. Rose has kept her inherited assets in her own name. But the two women share a lot--a house in West Los Angeles, a car, two dogs, a cat and an explicit agreement on how they would divide things if they split up.

“I think some people mistake the way they hold assets with the degree of commitment,” said Greene, a financial analyst, who sees in her job the damage wrought by what she calls indiscriminate merging. “I don’t think I love Carol one iota less because I choose to hold assets in my own name.”

Others, however, are wary of such separateness. They fear it symbolizes bad faith. Some say they would never marry a man who asked that they sign a prenuptial agreement; indeed, weddings have been called off at the last minute over that issue.

“I’m certainly suspicious of people who really keep things separate,” said Sarah Williams, the 41-year-old television executive who pays all of her husband’s living expenses. “I mean, joining funds is like the least of the commitment to joining your lives together.”

And a few, like Jeannette DeWyze, prefer to keep everything totally separate.

“I think in the early years of my marriage I was very concerned about preserving my own autonomy within the union,” said DeWyze, a 37-year-old writer. “I guess it was always important for me to feel I could make it on my own outside of marriage.”

“It just fit us, and our psychological makeup,” she said. “It’s only from other people’s reactions that I get some idea of how weird people think it is.”

TIPS

* Couples should talk about money in advance because the consequences of non-decisions can be dire. Ex-partners can find their hard-earned assets split 50-50 under community property laws or passed on, inadvertently, to a surviving spouse’s children from a previous marriage.

* Under California’s community property system, money earned through either spouse’s work during the marriage becomes community property. If the marriage ends, those earnings must be served up for division under the terms of a divorce settlement.

* Assets acquired by either spouse before the marriage can be held as seperate property-not subject to division in a divorce-as long as an absolute separation is maintained and there is no intentional or inadvertent “commingling” of assets.