The Arlington County Board has approved the creation of a non-profit housing corporation that will permit a coalition of tenants seeking to turn their apartment complex into a cooperative to sell $6 million in tax-exempt notes to finance the project.

At a meeting last Saturday, tenants of the 114-unit Marlo, Arclo and Radnor buildings, which overlook the Iwo Jima Memorial, told the board that without approval of the corporation, their homes would be converted to high-priced condominiums which virtually none of them could afford.

The corporation will sell short-term notes to financial institutions in order to obtain a low-interest construction loan.

Approval of the corporation is regarded as a major step by other tenant groups in Arlington which, like the District of Columbia, is losing large chunks of once-abundant, moderate-cost apartments to condominium conversions.

Because of its many subway stops and its proximity to downtown Washington, Arlington currently has the lowest apartment vacancy rate of any suburban jurisdiction and has lost more than 25 percent of its housing stock since 1972 to condominiums.

Tenant leader Colette Collier told the board that the group's option to purchase the property expires May 5. By that date, the group must raise $180,000 in cash from tenants interested in purchasing shares in the cooperative, which must receive final approval from the U.S. Department of Housing and Urban Development.

Collier said residents of nearly 50 units have each agreed to put down $2,000 toward purchasing a share. The estimated monthly payment for a one-bedroom unit, including utilities and possible major repairs is $440, a figure that doesn't include the tax benefits of ownership. About 20 percent of the residents would receive federal subsidies to ensure that they pay no more than one-quarter of their income for rent.

Among those eligible for the subsidy is Katherine Gee, who said she and her blind, 91-year-old aunt had searched for comparable housing and could find nothing for less than $400 per month.

"I've had two heart attacks and a cancer operation," said Gee, 71, who told the board, "Here are of a couple of, I hate to say it, old ladies . . . who will have no place to go" without a cooperative.

When board member John W. Purdy questioned whether the monthly payments could really be considered moderate cost, county housing supervisor Edward B. Brandt replied that he "didn't like those numbers either."

Brandt pointed out that total monthly payments at Claremont, a condominium in South Arlington, presently total at least $800 per month.

"Let's face it," Brandt said, "Arlington is a hot place to live."

Board member Dorothy T. Grotos was the only board member to vote against the corporation, saying she did not think the project had received adequate consideration by the board.

In 1978 the board, at the request of Arlington Hospital officials, created an industrial authority to permit the hospital to be refinanced at preferred interest rates.