“Free” carries a hefty price tag.

Socialist Zohran Mamdani’s lofty promises of an affordable, progressive Big Apple have electrified throngs of voters — and terrified others concerned about its costs.

The far-left Democrat’s policy proposals will need at least $10 billion and could fundamentally reshape the Big Apple’s economy and government.

Here’s how New York City could change under a Mamdani mayoralty:

Higher taxes on the rich and corporations

Mamdani’s sweeping policy goals are largely hinged on a “tax-the-rich” promise.

The Queens assemblyman proposes to raise taxes on millionaires by 2% and hike the corporate tax rate to 11.5%.

Doing both would raise roughly $9 billion, his campaign contends.

NYC mayoral candidate Zohran Mamdani has campaigned on promises of a more affordable Big Apple. Aristide Economopoulos

Groups of supporters have advocated for Mamdani ahead of Election Day. Michael Nagle

But a mayor can’t magically raise those taxes — Mamdani would need state lawmakers and a skeptical Gov. Kathy Hochul to take action in Albany.

Hochul, who will be fighting for re-election in 2026, has echoed the bellyaches of New York bigwigs that raising taxes would only drive the wealthy and businesses out of the city.

She has instead promised to find ways to cover the tab without taxing the rich.

Mamdani has even admitted he could need to find a Plan B for funding his plans.

“If this money is funded by the additional taxes or it’s funded by a better-than-expected (tax) assessment, or it’s funded by a pot of money that wasn’t previously spoken about, or savings that have come in, then the most important thing is that it’s funded,” he said.

Freezing the rent

“Freeze the rent” is a central plank of Mamdani’s campaign, but it’s not so simple.

Mamdani’s proposal actually applies to tenants in rent-stabilized housing, about 2 million New Yorkers.

As mayor, Mamdani pledges to stack the powerful Rent Guidelines Board — which handles decisions on rent-stabilized apartments — with hand-picked appointees who’d nix any hikes, much as his favorite living Mayor Bill de Blasio’s board did three times.

The Queens assemblyman says his “freeze the rent” plan would help struggling tenants. Kevin C Downs forThe New York Post

The move would help tenants struggling to make ends meet in the nation’s most expensive rental market, Mamdani maintains.

Critics contend this will only increase costs for apartment owners, who could take units off the market — thus indirectly raising rents citywide.

Mamdani’s critics argue that the controversial rent-freezing policy would actually lead to higher costs for both apartment owners and tenants. William Farrington

Mamdani’s rival Andrew Cuomo has argued the socialist can’t actually promise to freeze rents because it’s up to the board, while lame duck Mayor Eric Adams is eyeing packing it himself with appointees who’ll foil any “rent freeze.”

Free buses

New Yorkers in Mamdani’s progressive utopia will ride “free and fast buses.”

The campaign promise jumps off Mamdani’s main accomplishment during his three terms as a state lawmaker: starting a pilot program for five MTA bus lines.

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The program increased ridership and actually made buses safer, as bus drivers didn’t have to confront fare box scofflaws, Mamdani contended in an op-ed for The Nation.

Mamdani proposes to expand it citywide — with a $700 million price tag — as a way to ease the burden on working-class New Yorkers who can’t afford the fare to make it around the city.

The proposal was memorably slammed by the Washington Post’s editorial board as a recipe for turning buses into roving homeless shelters.

However, critics have cautioned that the free bus plan would be more expensive than the democratic socialist has advertised. Getty Images

“Vagrants and drug addicts would camp out all day on New York’s buses, especially in the winter,” the scathing op-ed read.

MTA honcho Janno Lieber recently pumped the brakes on Mamdani’s promise, arguing it’d be more expensive and harder to pull off than advertised.

Universal childcare

Mamdani plans to shell out $6 billion to provide universal, free childcare to New York City families — the most expensive of his plans.

The long-held progressive dream has received some support from Gov. Kathy Hochul, who signaled she’d work with Mamdani to make it reality — even as she rejected his proposal to fund it by taxing the rich.

Mamdani plans to spend $6 billion on his universal childcare plan. Michael Nigro

But Hochul wouldn’t offer any clue as to how she’d help pay for their shared goal.

Mamdani also proposed shelling out roughly $20 million to provide free “baby baskets” containing diapers, wipes, nursing pads, swaddles and other essential newborn goods for the 125,000 babies born every year in the city.

City-owned grocery stores

Five city-owned grocery stores would sprout up across as many boroughs if Mamdani has his way.

Mamdani envisions the stores selling groceries at wholesale prices to alleviate skyrocketing costs for New Yorkers with lean checkbooks.

The controversial politician also plans to open five city-owned grocery stores. William Miller

The idea, however, has been panned by bodega and grocery owners — including billionaire Gristedes owner John Catsimatidis — as a looming “Soviet”-style disaster that would drive them out of business.

Other critics pointed out that other city-owned grocery store experiments, notably one barren wasteland of a shop in Missouri, show the idea has no shelf life.

Department of Community Safety

A new, $1 billion Department of Community Safety would oversee mental health calls rather than cops under Mamdani’s public safety vision.

Mamdani, who has disavowed his past support for defunding the police, contends the new department won’t be funded by cutting from the NYPD.

The department would increase mental health outreach teams in subways and beef up “gun violence interruptor” programs.

The effort would free up cops to do actual police work instead of dealing with the “failures of the social safety net,” Mamdani argued.

But many public safety experts contended that cops ultimately still will end up having to pick up the slack dealing with unhinged, sometimes dangerous New Yorkers — making the department both expensive and duplicative.