Most people who have bought home along the 1-270 corridor have two things in common: They wanted to live in Montgomery County, and the corridor was the only part of the county they could afford.

Many have other things in common. They tend to be under 30. They either have young children or plan to have them soon. They work in the county. And they grew up in suburbs, not cities, most often in Washington's closer-in surburbs.

Relatively few of the residents of the corridor are single or elderly. Almost none is a member of a minority group. Almost none of the families has an income of less than $15,000 a year.

One recent evening, three families gathered in the living room of a six-month-old town house to discuss life on the 1-270 corridor. The families have all recently bought town houses in the McKendree I subdivision of Montgomery Village, near Gaithersburg. The subdivision opened in September.

Tom and Jeannie McKinstry both grew up in Montgomery County, but in Rockville and Wheaton, respectively. They say they will never again live "down county." They also say they do not intend to stay in McKendree. In five years, they hope to have bought genuinely rural property in Frederick County.

McKinstry, 26, works for the Pinkerston detective agency in Silver Spring. His wife, 25, is a registered nurse who works parttime at Montgemery Geranel Hospital in Olney. They have a daughter, Heather, 2.

The McKinstrys' two-bedroom town house is their first home. Previously, they lived in an apartment in Gaithersburg. They moved in December.

"We were taken by the charm," said Mrs. McKinstry. "Where else can you see the country?"

The McKinstrys paid $32,000 for their semi-attached home. They were able to afford it, they said, because they were required to put only 5 per cent down. But meeting monthly payments has proven difficult. Theirs, including utilities, often run to $600 a month, they said.

Because McKendree home prices are relatively cheap, the subdivision had a reputation in Montgomery Village and the area as a future slum. To some extent, it still does.

Mrs. McKinstry said a woman told her sister-in-law in the village mall recently: "I just won't have my children going to school with any of those McKendree children."

But within McKendree, there is no such elitism. "We are all young couples, starting out in starter houses, just trying to make it," Mrs. McKinstry, said. "I love this house. We all have to start somewhere."

Bob and Sue Smith were living in a Montgomery Village apartment when Kettler Brothers, the developer, first announced plans for McKendree in October 1974. They were put on a list, "and we just kept calling," said Smith, 28, an accountant.

The Smiths bought because they are expecting their first child this summer. "We were living in a one-bed-room apartment. It was obvious we had to move somewhere," said Smith.

Traffic is a monumental struggle for Smith, who works in Bethesda, and to a lesser degree for his wife, 28, who works as a nurse in Olney with Mrs. McKinstry.

Smith leaves home at 6:45 a.m. each weekday to beat the morning rush. "By 10 of, it's all over," he explains. Coming home, he waits at the office until 6:30 p.m. to avoid the heart of the evening rush. The trip takes him about 20 minutes each way. If he tried to travel during peak hours ,it would take him as much as 40.

"Yes, it's insane," Smith admits. "I look into the future, I still see a traffic mess.

"But no one else has access - if they're having a tough day - to go down and look at ducks on a lake."

Betty Sasso and her husband, John, are a career Navy couple. In 22 years, they have lived "in so many places, I lost count," Mrs. Sasso said.

They bought at McKendree after unloading an "enormous" eight-bedroom house in Rockville. "My husband and I were a little tired of subsidizing Pepco, now that the kids are gone," Mrs. Sasso said.

Mrs. Sasso first considered McKendree when she was helping a daughter and her husband move into an apartment elsewhere in Montgomery Village last year. The development "seemed progressive, perfect for us," she said. Her husband, now retired from the Navy, works as an executive for a government contractor in Rockville. She is an accountant for a Rockville computer company.

The Sassos bought a four-bedroom model of the standard two-bedroom McKendree town house, "in case there are grandchildren." I cost $35,000, only slightly more than the other model.

Mrs. Sasso said she does not mind being one of the few people in McKendree older than 35. "I love kids," she said. "Age is a mental thing.

"I don't see any reason why we can't be happy here," she said. "It's a differnt feeling when you drive in here. I did my time mowing the lawn."