Here’s a hot real-estate tip for anyone out there with a few million extra dollars lying around (which at this point is Warren Buffett and that’s pretty much it). Go and buy something in One Fifth Avenue. Quickly. Take out a loan. Cash in that quarter-tank of gas. Do whatever it takes, because that landmark building in the Village’s so-called Gold Coast is set to become the most scrutinized, most gossiped-about, most popular piece of real estate in Manhattan.

“One Fifth Avenue” is the title of Candace Bushnell’s upcoming novel, and critics can debate all they want about the “Sex and the City” writer’s literary skills, but there’s one thing that’s not in doubt: Where she goes, her army of stilletoed fans follow. If you have any doubt about her ability to popularize concepts in mainstream culture, just look at how ubiquitous (and insufferable) cosmos and the Meatpacking District became. Look at how everyone in society has become a sex columnist since Bushnell’s musings first appeared in 1994.

Now she’s turned her word processor to One Fifth, a 27-story art-deco tower that was built in the 1920s and has been home to celebrities, artists, writers and other well-to-do types for years. As the book’s back cover blurb breathlessly explains, “One Fifth Avenue is the building – the chicest, the hottest, the best pedigree, with all the most interesting people. Within its thick, pre-war walls, the lives of New York City’s elite play out.”

Well, not quite, according to residents interviewed by The Post. But of course, like most of Bushnell’s work, her latest is heavily fictionalized reality. And like most of her other work, it offers a voyeuristic glimpse into the lives of the rich and privileged. The middle class do not exist in Bushnell’s world. The lower classes do, but their appearance begins and ends with the delivery of finger sandwiches somewhere around Page 400.

The plot of “One Fifth” revolves around the intersecting lives of various residents. Mindy Gooch is the severe board president whose marriage to her wimpy writer husband, James, is failing. Philip Oakland is an acclaimed screenwriter and a twice-divorced playboy with a taste for young women. Schiffer Diamond is a middle-age actress and Philip’s former girlfriend who may be out to rekindle the romance. Paul Rice, the building’s newest resident, is an obscenely rich hedge-fund manager whose extensive renovations antagonize Mindy and his neighbors.

In between, brand names get dropped, $2,000 boots get bought, fancy French meals at La Grenouille get consumed, and helicopters get taken to the Hamptons.

Anyone else smell a hit?

Sara Nelson, editor-in-chief of Publishers Weekly, says the book should become a best seller upon its release in September.

“It will be interesting to see how it does, now that the ‘Sex and the City’ days are pretty much over,” she says. “It’s interesting to note, though, that while ‘Sex and the City’ was Bushnell’s first book, and the title with which she is most identified, thanks largely to the TV series, her subsequent books were actually more successful in terms of sales.”

And although a publicity storm for the building is probably imminent, someone forgot to post that info on the laundry room bulletin board. None of the residents The Post spoke to even knew the book existed. Are they worried?

No, says John Knoebel, an 11-year resident who works in publishing. “There’s nobody in the building that would be so caught up in their wealth, ego and security that they’d complain about the book,” he says.

Paul Gigante, a five-year resident and former board president, says that, as an ad man, he can appreciate the value of publicity.

“How many other buildings get books written about them?” he asks, but adds that the residents will embrace the novel only if its fictionalized characters don’t hedge too closely to actual denizens.

“I’ve been there for a while, and I’m not aware of any kind of particularly salacious things going on,” he says. True enough. The biggest kerfuffle seemed to involve a resident suing the board to move a 2-inch steam pipe all of four feet.

Which raises the big question about why Bushnell chose this particular building as the book’s setting.

An examination of property records reveals that the address has an interesting mix of doctors, lawyers, writers, art collectors and senior citizens, but what higher-end building in the Village doesn’t? And yes, a few celebrities reside there, but they aren’t exactly the glamorous kind paparazzi follow around: Jessica Lange and Sam Shepard (who live in a $3.5 million pad), Blythe Danner, Tim Burton and Helena Bonham Carter, and film director Brian De Palma. Brad Pitt and Gwyneth Paltrow once crashed there, but that was long ago.

And it’s not like the apartments inside are ridiculously sprawling. One Fifth began life as a hotel, so most of its units are one-bedrooms, though there are a few combined multibedrooms. Still, nothing even close to approaching the digs described in the book: a sprawling, grand triplex, complete with a ballroom – not unlike the penthouse at the Sherry-Netherland.

Most likely, Bushnell (who declined an interview request) is using the building as a generic representation of any building in her world. The fact that One Fifth has an iconic exterior and a long history also helps. “The building [holds] a fascination [for] a lot of people,” Gigante says. “It’s an inspirational place. It’s got a heroic kind of thing. If you were going to build a story about a place, it’s a good as place as any to write about.”

Bushnell nearly wrote herself into the story, it seems. Building resident and real-estate agent Anna Bayle says the writer looked at an apartment for sale in One Fifth a couple years back – though it’s unclear if she was simply doing research.

When readers finally begin devouring pages, many will no doubt be guessing if the book’s characters are thinly veiled representations of actual New Yorkers (see story above). The guessing game could last for years, because most all of the characters are vaguely drawn enough to suggest a number of possible stand-ins – if that is Bushnell’s intention, which is not necessarily a given.

One character not veiled in the least is Thayer Core, a reporter for media gossip blog Gawker. Of him, Bushnell writes, “Thayer Core was a bully, and like most bullies, he lacked courage. He was far too fearful to take physical action, striking out at the world instead from behind the safety of his computer.”

Gawker managing editor Nick Denton says he’s “flattered and amused that Candace Bushnell would cast a Gawker writer in the role of a hack without a conscience.” Denton says that the author, whom he describes as a former journalist who’s become “part of the establishment,” is simply returning the favor for the times the site has written about her.

You gotta love it: the conflict, the secrets-telling, the peek into the world of the rich and valueless. It all adds up to a juicy summer read, albeit one that comes out in the fall.

reed.tucker@nypost.com

The real one fifth

* Height: 27 stories

* Built: 1920s

* Became co-op: 1976

* Architect: Harvey Wiley Corbett, who also designed Met Life’s North Building at 25 Madison Ave. and the Manhattan Criminal Courts Building at 100 Centre St.

* Average current price per square foot: $1,918

* Most expensive apartment currently for sale: 4 bed/4 bath for $8.75 million

* Most famous former tenants: Gwyneth Paltrow and Brad Pitt

* Most famous current tenants: Jessica Lange and Sam Shepard

* Second most famous current tenants: Tim Burton and Helena Bonham Carter

* Big building issue: More than 60 years of coal dust had to be cleaned off the exterior recently.

Who’s who inbuilding roster

Unlike some society novels, “One Fifth Avenue” isn’t a thinly veiled roman à clef. But a few telling details make us wonder if some of Candace Bushnell’s characters weren’t at least partially inspired by real-life New Yorkers.

* Could the book’s Billy Litchfield, a fashionable art dealer who socializes in the upper class but doesn’t quite belong, be based on Bushnell’s former Observer colleague and Vogue editor-at-large William Norwich? Norwich, like the book’s Billy, is tight with society ladies.

* Enid Merle, an aged, “nice” gossip columnist with ties to society, sounds a bit like The Post’s own Liz Smith.

* Mrs. Houghton, a superwealthy arts patron, dies and leaves behind a gigantic apartment, which various parties squabble over. Brooke Astor anyone?

* Is Schiffer Diamond meant to be Jessica Lange, the real One Fifth’s only middle-age actress tenant? Diamond is romantically linked to Philip, an award-winning writer just like Lange’s beau, writer-actor Sam Shepard. And coincidentally, Philip is described as having once been a ballet dancer; Lange once dated Mikhail Baryshnikov – who also played a major role in “Sex and the City.”

* Is Annalisa Rice (which we think sounds a lot like Condoleezza Rice), the society-loving wife of a banker, meant to equal Marina Rust, author and fixture about town? The last names are nearly identical and Rust, like Rice, has roots in Washington and is married to a Georgetown-educated banker (in Rust’s case, Ian Connor).