COMMITMENTS : Crowd Control : Taking on a roommate is like going on a blind date that doesn’t end after one night. But a lot of people are finding good reasons to take the plunge.

The worst-case scenarios rival scenes from “Single White Female,” the 1992 film in which a woman finds out her female roommate is dangerously unstable.

Alicia Lynn, 28, of Santa Clarita, says she has experienced her share of unpleasantness with roommates--including the suicide of one a month ago in the condominium she shares with her boyfriend and two other male roommates.

“You can never know someone completely,” Lynn said. “It’s scary trying to screen people before they move in.”

Having roommates has been likened to a blind date that doesn’t stop after one night--an arrangement born primarily out of financial need, but risky because one, literally, has to live with it. And many people do.

More than 4 million people in the United States reported themselves as a roommate or housemate in the 1990 U.S. Census Bureau survey. In Los Angeles County, where single apartments often cost $500 or more a month, the figure was almost 300,000. Classified ads in area publications are full of those seeking to share rentals or who have rooms for rent.

Roommates seeking roommates are mostly young professionals, generally between the ages of 20 and 40, according to Roommate Finders and Roommate Express, two Los Angeles roommate-matching services.

“A lot of people need that extra income,” said Christine Peacher, manager of Roommate Express in Costa Mesa. “That extra $400 helps.”

Gwenevere Young, 24, of Los Angeles, said she could never go back to living in a single apartment after sharing a spacious Spanish-style house with three other women, each paying about $350 a month in rent.

“I am spoiled to be living here,” said Young, an assistant in the home video department at Orion Pictures. “I’ve looked at single and one-bedroom apartments, and I really appreciate what I have here. It’s such a great house.”

But while roommates may alleviate financial burdens, they can add a whole set of personal issues that need to be addressed. With several separate lives existing under the same roof, conflict can occur.

Young said she would encourage people not to live with friends.

“Friends will find whatever weakness you have and leech onto that,” she said. “They will take advantage of you.”

She recalled one male roommate, no longer living with her, who never cleaned up after himself, ate other people’s food and never contributed household items, such as light bulbs.

“He was very negative. He didn’t care about anything. I had to hound him about the bills. He would say things like, ‘It’s not my house. You deal with it,’ ” she said.

Sharing space can be a breeding ground for a number of problems. The key is communication, said Nancy Tither, a clinical psychologist and director of Associated Psychological Services of Encino. “Roommates need to be more skilled than a husband and wife in negotiation skills. Because in a romantic relationship, roles are more understood.”

Tither said that often roommates unconsciously re-create their original family, where one person may have been used to having someone clean up after him and still expects someone to do that. “The important thing is that roommates have equal voice and equal power.”

Guidelines should be set early. Potential roommate problems revolve primarily around whether someone is able to meet the financial responsibility and struggles over the highly used rooms in the house, she added.

“Intrusions occur where people step over commonly assumed boundaries,” Tither said, explaining that not cleaning up, eating other people’s food, not giving equal time in a shared bathroom and not fairly sharing a living room space can cause friction. “It’s important to address any problems in their incipient stages.”

While roommates may dismiss their arrangement as one of financial need, it’s still very important that they get along. And that hinges on a person getting to know a potential roommate before living together, Tither said. “If you’re having trouble with a roommate, it can affect your ability in school or at your job. It’s a very important choice.”

Janeen Rae Heller, a young professional guitarist, interviewed about 20 people who answered her ads in the L.A. Weekly, Los Angeles Reader and the Recycler before she found her roommate, a woman who offered to share her apartment in Burbank.

Heller, a vegan--that is, a strict vegetarian--was looking for another vegetarian to live with.

“It’s a completely different lifestyle, and it’s important to me in my home,” she said. “I feel strongly about animals. I don’t want my friends in the fridge and I don’t want to smell them cooking.”

In addition to questioning potential roommates on the issues of vegetarianism, Heller’s interviewing covered age and maturity levels, autonomy, sleeping habits, noise levels and whether they would have boyfriends, girlfriends and others around a lot of the time.

“If you don’t go in depth, you don’t find out these things,” she said. “For example, I was an hour into a conversation with a man before he told me he was a naturalist and doesn’t wear clothes around the house.”

At Heller’s request, the man said he would be willing to wear boxers around the house, should they become roommates. Heller said she respected the man’s lifestyle choice, but when he asked her to come over in person and conduct the rest of the interview in their underwear, she drew the line.

“I was not going to interview in my panties,” she stated firmly.

Heller lived alone for 10 years, but was so disturbed by the isolation she experienced after the Jan. 17 earthquake that she felt the need to have a roommate.

“The new me wants to know someone’s coming home at night,” she said.

Among a growing senior population who may have lived most of their lives without roommates are individuals seeking housemates for social and economic reasons, said Margaret Harmon, executive director of the National Shared Housing Resource Center in Vermont. There are more than 350 programs around the country devoted to shared housing, and research is being done to document actual numbers of seniors in this type of living situation.

Joan Bauer, coordinator of Shared Housing at Valley Storefront Jewish Family Services in North Hollywood, matches seniors and non-seniors in shared living situations. She said an increased number of seniors in the San Fernando Valley have wanted to live with others since the earthquake because of fear of living alone.

“Often the senior is a homeowner whose family is gone and wants to stay in their home, so they want someone to come share the house,” Harmon said.

Physically and mentally, living together has positive effects on seniors, Harmon said.

“Their nutrition is better. They may not cook for themselves when they are alone,” she said. “And there isn’t the depression from loneliness.”

But some in the younger generation think roommates can negate one’s quality of life.

When Henning Lindblad, 24, got out of the Royal Swedish Navy at 21, he never thought he’d “share the same sleeping space with someone else except a person of the opposite sex.”

But as a student living in the dormitories at California State University, Los Angeles, the fiscal reality of spending $460 for a single room versus spending $312 for a double-occupancy room gave Lindblad the incentive to share living quarters again as he had in the military. But things didn’t work out with his roommates, souring him on the idea.

He said his grade-point average and quality of life have improved since he moved--alone--into a studio apartment in Alhambra: “I’d rather donate my blood for money or go to the Salvation Army to beg for food than put myself in a roommate situation again.”