If you live in New York and happen to have about $625 in your pocket, you could go out and buy yourself a plane ticket to Los Angeles, a 32-gigabyte iPad, or perhaps a shiny pair of Christian Louboutin pumps. Or you could make that your monthly rent in a city apartment, by sticking with Sophia Cosmadopoulos.


Ms. Cosmadopoulos works not in real estate, but in the field of art therapy and instruction, and she has plenty of student loans to pay. So to make ends meet in this city, she has worked odd jobs, eaten many $1 tacos and chased low rents around Brooklyn, keeping that expense consistently hovering around $625 per month, give or take a few tacos.


While her budget has remained constant, rents in that borough have emphatically not. Following Ms. Cosmadopoulos’s path — from the edge of the Brooklyn-Queens Expressway in Carroll Gardens, to Williamsburg, then Bushwick, and finally to Bedford-Stuyvesant — creates a rough map of rising rents across parts of Brooklyn.


“They’re not glossy, and they’re kind of falling apart,” Ms. Cosmadopoulos said of her various apartments, as she sat sipping tea at her narrow kitchen table. She also has been forced to forgo the luxury of living by herself. “But I’ve always valued what I could get out of New York, more than where I lived.”


There are still areas outside Manhattan where a $625 apartment or share can be found, but those pockets have moved farther and farther inland. And in Manhattan, that particular price tag is all but gone. A search on Craigslist last week for a $625 maximum rental in Manhattan turned up just one lonely little listing, for a single room in Harlem. No smokers, please.


“I think if you go back to 1992, give or take, that’s the last time you could potentially find something in that price range” in Manhattan, said Gary L. Malin, the president of Citi Habitats. (In 1992, Ms. Cosmadopoulos turned 7.) Today, Mr. Malin said, “the cheapest thing in Manhattan that’s shareable is $1,050 to $1,100 per person, and we’re talking about a tiny walk-up.”


Many young people, of course, are thrilled to take the stairs or sleep stuffed in a crawl space so they can afford to live in New York. And Ms. Cosmadopoulos readily admits that while all of her apartments have had pleasant, old-fashioned qualities, they have also had drawbacks. One was a sixth-floor walk-up, another a four-bedroom railroad flat, two had many-legged visitors, including lots of water bugs and one rat, and all were in a general state of decay.


In her current apartment, for example, which has hammered tin ceilings and decorative fireplaces, a chunk of the bathroom ceiling came down recently, leaving a hole the size of a small pizza box above the toilet. While she and her roommate were examining their new air vent, they found a stash of pages torn from 1970s pornographic magazines.


“It’s nice to live in an apartment where you have stories,” she said with a giggle.


Her rent is $650 per month.


Jonathan Miller, president of the Miller Samuel appraisal firm, said the last time he had paid a similar amount was in a western suburb of Chicago in 1984, and at the time, he said, he thought his one-bedroom apartment was fabulous. Twenty years later, however, he drove by to take a peek at it with fresh eyes.


“I looked,” Mr. Miller said. “And I thought: ‘Oh. What a dump.’ ”


Ms. Cosmadopoulos, who says her childhood in San Francisco prepared her for New York’s real estate madness, might already use the same word to describe her first place in Brooklyn: a three-bedroom basement apartment by the B.Q.E., a 12-minute walk from the Carroll Street stop on the F train.


“We would literally find like three water bugs a day,” she said. “That was not ideal.”


Her portion of the rent was $550 a month, but she and her two roommates decided that even that was too much, she said. They broke the lease, and she moved into a two-bedroom, sixth-floor walk-up in Williamsburg, near the Lorimer Street stop on the L train, where she paid $675.