For Richer or for Poorer, in Up Cycles and in Down . . . : Entrepreneurs: Husband-and-wife teams are the fastest-growing segment of the small-business population. But it’s not all hearts and roses.

Around Valentine’s Day five years ago, Don and Maggie West put their young marriage to a very tough test: They became business partners.

The Wests ate, slept and breathed business with each other, she as chief executive and he as president of House of Batteries in Huntington Beach. Together they struggled over employees, equipment purchases and every other aspect of their company. Through it all, sales increased 20% annually.

And their marital relationship?

“We’ve probably grown 50% each year,” said Maggie West, who is the accountant of the two. “We’re more dependent on each other. I can understand his moods more so . . . because I’m in the trenches with him.”

The Wests represent the fastest-growing segment of the small-business population: entrepreneurial couples. Businesses owned jointly by couples now total almost 500,000 nationwide, nearly double that of 1981, according to the Small Business Administration.

In Southern California, the number of husband-and-wife enterprises has grown because the recession and subsequent layoffs have forced many people to start their own businesses or to join their spouses at family-owned shops, employment experts say.

Whereas the Wests have made the most of their arrangement, combining work and wedlock has proven perilous for others, and it isn’t recommended for everyone, family counselors say. Indeed, Santa Barbara business psychologist Ralph Daniel said being in business together is like “sailing in fast waters.”

“It can be incredibly gratifying, exhilarating,” said Daniel, who has counseled hundreds of entrepreneurial couples during his 20 years in practice. “But it can also be stormy and tumultuous.”

Judy Harman, associate director of Cal State Fullerton’s Family Business Council, recalls a middle-aged couple who had bought a tile business in Garden Grove. The couple had been happily married for 15 years until they began to operate the business together.

“They just saw things in each other they never saw before,” Harman said. “Her complaint was that he was less principled than she thought. And his was that she criticized him all the time.” After two years, both the marriage and business dissolved. “The business did them in,” Harman said.

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So what makes for a successful blending of entrepreneurialism and amore ? For many couples, it starts by designating separate duties for each other--as Cynthia and Ray Navis did when they founded the Upper Crust, a golf-accessories company in Solana Beach near San Diego.

The Navises, who met at the Los Angeles Athletic Club and have been married seven years, built their business five years ago based on her design for a fashionable golf hat. The company expects sales of $800,000 this year.

Cynthia, 29, handles the design and production of the products. Ray, 37, takes care of all the marketing and financial work. They drive to work separately and have separate offices.

“My wife is artistic and my background is financial,” Ray said. “You don’t have to be good at everything.” Another benefit: “If you’re running a business with a relative, there’s a trust factor you don’t have to worry about.”

Even with clearly defined roles, though, conflicts are unavoidable, especially when it comes to issues of money, management roles and long-term strategy--the three most common problems among family businesses, according to a recent survey sponsored by Massachusetts Mutual Life Insurance Co.

Indeed, Don and Maggie West’s problems usually have had to do with purchasing, such as the time he wanted to produce color brochures at a cost of $40,000 and she balked. Eventually, Maggie, now 39, relented, but only after the couple took their differences to their accountant, who helped them solve the problem.

“You need outside advisers,” said Don, 47. “There’s no way you can make the right decisions by yourselves all the time.”

Frank and Silvia Garcia, the longtime co-owners of La Casa Restaurant in Anaheim, say they know each other so well that they can usually avoid arguments at work.

“This is red,” Silvia said, holding a bottle of Tabasco sauce. “But if Frank says it’s green, I say, ‘OK.’ ”

Frank admits with a smile that he blows up occasionally, but only for a short while. “We can’t argue a lot, because if we do the restaurant goes down,” said Garcia, who at 50 is nine years older than his wife. “And all of our help and our customers would look at us.”

Like most couples in business together, the Garcias say they take their work home with them, talking about the next day’s special and other affairs of the restaurant.

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But Patty Kishel, a marketing professor at Cypress College who has written articles on family businesses, advises entrepreneurial couples as much as possible “to just shut the door and say the office is closed.”

At home “it’s a marriage, not a merger,” Kishel said, noting that couples in business together should go out on dates--together. “You have to work harder to keep the romance alive.”