BALTIMORE - The shared purchase of a vacation home can reduce costs and make feasible outlays that otherwise would be unaffordable - providing the owners are compatible and there are no hidden conflicts.

Two Baltimore couples, Deborah and Mark Dopkin and Elissa and Stanley Hellman, bought an oceanfront townhouse in Ocean City, Md., a decade ago and split the cost. The arrangement gives each full run of the beach house while paying only half the utilities, fees and maintenance.

"Having partners is somewhat liberating - no guilt or sense of pressure to run to the beach if you do not use the house all the time," Deborah Dopkin wrote in an e-mail.

With the typical beach-vacation home used by its owner fewer than 30 days a year, co-ownership has become a tradition because it eases the financial burden of a second home and also rewards homeowners with many of the benefits.

"It happens quite consistently down here," said real estate agent Grant Fritschle, of the Mark Fritschle Group of Re/Max Premier Properties in Ocean City.

Sometimes relatives pool resources for a beach house or condo. Sometimes friends do. Agents estimate that a small percentage of the area's beach homes are co-owned.

The emotional pull of a retreat aside, the top reason to buy together is financial.

"This gives them an opportunity to own half the property and have half the expenses and have full enjoyment," said Joyce Henderson, a Coldwell Banker agent in Bethany Beach, Del., who sold the Dopkins and Hellmans their home. "It's sort of the best of both worlds. I wish more people did it."

A big question is how to make joint ownership work, with or without a written agreement.

Compatibility and flexibility are what matters. A compatible vision for use, for change, for housekeeping and for dividing expenses are key, as is the ability to think of co-owners - whether friends or relatives - as business partners.

The Dopkins and Hellmans knew each other for years before they talked about buying. "We didn't want to put a lot of cash in when we could share the burden," Deborah Dopkin said.

The baby boomer-ish friends, three of whom are attorneys, drew up legal ownership and financial paperwork. Mostly, their agreement relies on being agreeable.

The couples created a separate taxing entity with a bank account they replenish as needed. They split responsibilities. They consult each other on big expenses, such as new flooring; when something breaks, whoever is there tells the other and arranges repairs. Summer is for renters, as both couples prefer the beach in the less-crowded spring and fall.

They alternate the "holidays" - Memorial Day, Maryland State Bar Association convention week and Thanksgiving.

"We have one nice little rule: When you leave, you make sure the beds are made," Stanley Hellman said. "With fresh linen."

That each couple likes doing different things at the beach is irrelevant. They stayed there together once, right after buying the house in 1999. But since then, they've stuck to their pact that each couple gets the privacy of getting away without the other.

Real-estate agents and lawyers recommend the couples' thought-out approach because it forces people to consider more issues. Agents say while loss of interest is the top reason for selling, failed marriages, decorating clashes and belatedly uncovered incompatibilities create friction.

"The same issues arise no matter how the property is titled," said Gregory Reed, a partner in Ballard Spahr Andrews & Ingersoll in Baltimore who teaches real estate law at the University of Maryland School of Law.

Among the issues: how decisions are made, who can use the property when, allowing rentals and how expenses will be paid.

Head off disputes and surprises by airing expectations, setting rules and deciding ownership and financial structures, he said.

"With beach property, there is a little bit of a tendency to be less formal about how you document this stuff," he said, noting that even an informally written agreement is a plus.

Owners should anticipate financial shortfalls and what happens if one wants to sell, he said.

Ultimately, any co-ownership plan has to work for each owner's lifestyle.