What's so funny about poverty, mental illness, and homelessness?

Many creative types make sacrifices for their art, but solo performer Ann Randolph takes the whole struggling artist bit further than most.

Now in her 40s, she says she's never paid rent in her life. Her possessions fit in a suitcase, she has lived in uncomfortable situations, and she has worked some really hard jobs to fund her creations.

But the commitment and struggle are paying off. ''Squeeze Box," a show about her experiences working the graveyard shift at a women's shelter in Santa Monica, won awards and attracted the attention of the late actress Anne Bancroft and her husband, Mel Brooks, when it was performed in Los Angeles. The pair produced it off-Broadway, where it ran for four months.

Directed by Alan Bailey, ''Squeeze Box" is now in previews at Merrimack Repertory Theatre and opens officially on Sunday night.

''The performance is very, very funny," says Charles Towers, artistic director of Merrimack, who chose the show after seeing it in New York. ''Then she can turn on a dime and move you to tears. She performs a half-dozen different characters, and she treats the women with enormous respect."

Randolph is used to unusual living and work situations. The Loveland, Ohio, native put herself through college by living in a state mental hospital and writing plays for the patients to perform. In Alaska, she gutted fish and cleaned oil-soaked rocks after the Exxon Valdez spill.

That job netted her $20,000, which she intended to live on while she worked as an actress in New York. But during the cross-country drive, she stopped in Santa Fe to see a friend and ended up using the money to build a rudimentary outdoor theater.

By now, Randolph was an old hand at living low on the hog. A year later, in the early '90s, she moved to LA and started performing with the improv comedy group the Groundlings. She worked at the Santa Monica shelter for $8.60 an hour, sleeping there three nights a week.

When her Groundlings buddies -- Will Ferrell, Cheri Oteri, and Chris Kattan -- moved on to achieve fame on ''Saturday Night Live" and elsewhere, she remained at the shelter.

''I didn't want to take a high-powered job," Randolph says by phone from LA. ''I just wanted to work with the homeless and do work that moved me.

''Part of my mission," she adds, ''is writing for people whose voices are not usually heard."

After she became itchy doing the Groundlings' three-minute sketches, she left the group to write her own material. In 2000, she started the pieces that eventually became her current show: ''Shelter," about Randolph's life in the shelter, and ''Squeeze Box," which explored her romance with an accordionist named Harold.

The characters are composites based on women she's encountered in her work: Brandy, the paranoid schizophrenic crackhead, who bangs on Randolph's window to wake her up; Irene, a Pentacostal preacher's wife, who was thrown out of her church after she sang about her husband's infidelities; and Julie, a right-wing do-gooder volunteer who ejects Brandy from a self-esteem class for using profanity. Harold is a composite of a man she fell in love with and an accordionist she heard once.

In the show, Randolph plays banjo, sings, and plays all these characters as well as a version of herself-- a woman who loves the work but questions both her own ability to do the job and to make it as a performer.

''I wrote it from the depths of losing complete faith that I would ever achieve success as an artist," she says. ''It asked the question, 'Why have I not progressed in life?' "

The title, she says, not only refers to the accordion but the fact that she was ''feeling that I had no choices in life at that point. Financially and artistically I felt in a tight squeeze."

Randolph created an evening out of the two pieces, and every time she had $500, she'd rent a theater for the night and perform them. Publicity was word-of-mouth. Even with no legitimate run, ''Squeeze Box" won the LA Weekly Theatre Award and the Ovation Award for best solo show in 2002.

That same year, Bancroft and Brooks saw the show. Afterward, Randolph says, the two came backstage and told her they wanted to make a feature film based on the show. Randolph said what she really wanted was for it to go to off-Broadway. They agreed to work on it with her and for the next 18 months slashed the two 70-minute pieces into a short, tight comedy about, as she puts it, ''homelessness, poverty, romance, and mental illness."

In a quote on Randolph's website, annrandolph.com, Brooks pays high praise. ''I've been around, and I haven't seen so much talent in one person since I married Anne Bancroft," he says.

Bancroft saw the show in New York and was talking about playing a role in the film they'd discussed. But on June 6, she died of uterine cancer. ''It was really difficult, very sad," Randolph says. ''She believed in the show and in me. And she had tremendous insight and a big heart."

Randolph is starting to write the film now. In fact, with Bancroft and Brooks's check for the movie and stage rights to ''Squeeze Box," Randolph for the first time is writing full time.

That's not to say she's now prancing around in Prada. All available money still gets plowed into her work, but now instead of renting theaters, she's buying equipment to make short films.

She still doesn't have a place of her own. For the last 10 years, she's relied on the kindness of a 21st-century version of a patron: a fan of her work who has helped her with rent or lodging.

At least Randolph has gotten an answer to the question she raised in the show about progress. ''What are we here for but to help one another?" she asks. ''I feel odd in speaking this way because it sounds so heavy; it's really a funny piece."

Catherine Foster can be reached at foster@globe.com.