When Kristi Barlow began looking for a new apartment in Brooklyn a couple of years ago, she ran into a familiar problem for New Yorkers with young children: she couldn’t find an accurate map showing, block by block, which neighborhoods were zoned for which elementary schools.

So she set out to make her own, a task that became something of an obsession. Eventually she created a map that satisfied her needs, as well as the cravings of her friends. And in February, long after she had settled into a new apartment in Park Slope, she turned her obsession into a small business and began selling maps of Brooklyn and Manhattan online.

Ms. Barlow would not be the first New Yorker to become utterly absorbed in the process of finding a home in a neighborhood with an acceptable zoned school. The mix of real estate and education has long been intoxicating in New York — and even more so in recent years, with the economy depressed and public school choices more alluring and complicated.

Ms. Barlow would not even be the first New Yorker to turn that obsession into a business. During the last decade, there has been a proliferation of school “consultants,” guidebooks and other commerce related to helping parents find the perfect school.

But for most parents moving into or around New York City, matching an address to a zone is Step 1 of their search, and resources are slim. The city refers parents who have questions about their move to the school in the area they are considering, or to the 311 information telephone line.

So people like Eleanor Kung, a 36-year-old freelance graphic designer who lives with her husband in Dumbo, Brooklyn, find themselves seeking out new sources of help.

Ms. Kung, who has a 15-month-old son, said she first heard about the maps in February on Bococa Parents, an online message board for families in Boerum Heights, Cobble Hill and Carroll Gardens. She bought the Brooklyn version.

“We had recently moved back to the NYC-area as first-time parents,” Ms. Kung wrote in an e-mail message, “and I thought I could use all the help I could get to navigate the public school system maze.”

Ms. Barlow, who works as a documentary film editor, initially created the map only for herself. Looking for an apartment in brownstone Brooklyn, she printed out a map of the neighborhoods near Prospect Park and outlined the zones for nearby elementary schools with a red pencil.

Friends with young children admired it, Ms. Barlow said, and when she found herself between editing projects late last year, she decided to revise her hand-drawn map and sell it online.

“I thought at the time I’d already done most of the work,” Ms. Barlow said. But, she added, “it ended up taking hundreds of hours to get this to the point where people could actually buy it.”

To build the maps, Ms. Barlow started with school zoning data from NYC Open Data, a Web site run by the city. She cross-referenced it with information she found on InsideSchools, an independent Web site that provides reviews of schools and is popular among parents.

But neither site had fully up-to-date information, she said. So she combed through Panel for Educational Policy reports for school zoning changes.

A few issues were never completely resolved, like a mysterious two-block area in Manhattan bounded by West 59th Street, West 60th Streets, Amsterdam Avenue and Central Park West in which the lines of the school district don’t match up with those of the local elementary schools’ zones. The anomaly is noted on the map.

“It’s a no-man’s zone,” she said. “I don’t know what you do if you live on those blocks.”

Deidrea Miller, a Department of Education spokeswoman, said the city’s School Search tool on its Web site has accurate information for schools that are currently open, but not for zoning changes that will occur as a result of new schools opening in the fall. In December, for instance, the city made a number of changes in Lower Manhattan that do not show up online.

Ms. Barlow sells both print and digital versions of the maps through her Web site, nycschoolmaps.com — $8 for a digital version and $20 for both a digital and laminated print version. She continually updates the digital one with zoning changes, of which she said there were at least two since she started the site. To keep up, she subscribes to every school e-mail listserv she can.

Her site also includes a section in which Ms. Barlow critiques other resources for information on zones. In March, she reviewed Sage, a new app that lets users enter an address and spits out the zoned school.

“Handy, sure,” she wrote, “but they apparently do not have the recent zoning changes in their database because they are giving out incorrect zones for some addresses.”

“In a nutshell, the criticisms are accurate,” said Edward Yau, the software engineer who developed Sage. Mr. Yau, who lives on the Lower East Side and has a 3-year-old, built his app using the city’s outdated data. Sage notes that parents should call 311 to double-check, he said.

For her part, Ms. Barlow now walks her son, Max, 7, to Public School 39 Henry Bristow in Park Slope. She has sold one to two maps a day since sales began, she said, and hopes eventually to cover her costs. At this point, she said, “I’m almost starting to think of it as a community service effort.”