There is rarely instant gratification when you’re the general manager of a franchise entrusted with building from the ground up, rather than inheriting a winning formula. George Young was hired on Feb. 15, 1979. It would be seven full years — and hundreds of absorbed slings and arrows — before his vision would begin to be realized.

Same with Frank Cashen, who was hired by the Mets before the 1980 season and four years into the job hadn’t seen the team finish higher than fifth place. Gene Michael had to get fired from the job as GM of the Yankees before the fruits of his labors were fully realized; Ernie Accorsi was a year into retirement when the Giants won the first of two Super Bowls for which he planted the fertilizer; Eddie Donovan was in Buffalo by time the two Knicks teams he built into champions actually won those titles.

It is a job, when it’s rewarding at all, that often saves its best rewards for the patient and the prudent, and reserves its biggest pratfalls for the impetuous and the impulsive.

Which brings us to David Stearns.

Stearns is the Mets’ general manager because Steve Cohen ultimately chose structure, and infrastructure, instead of an over-reliance on his checkbook. Stearns made his bones in Milwaukee. He is the Broadway show that started out of town, and wowed them in New Haven and Providence. Those shows, and those receptions, don’t always translate to the Great White Way.

But sometimes, they become “Hamilton.”

Cohen invested three years waiting for Stearns to channel Lin-Manuel Miranda, and $50 million once he was able to secure him. The ideal blueprint is that Stearns does what he did in Milwaukee — where the Brewers have made the playoffs five times in the last six years after making them four times in the 48 years before that — only with a platinum card, instead of a blue one.

The reality is trickier than that. He inherits a roster that — for all the millions spent last year — is incomplete, at best. He competes in the same division as the Braves — who’ve dominated the NL East the last six years — and the Phillies, who’ve won five playoff series in the last two. Both teams are well run. Both teams aren’t afraid to spend money.

(And if you have a Mets fan in your life, you know there is suddenly a lot of anticipatory angst afoot now that Jarred Kelenic is a Brave; we can call that “The Wheeler Postulate.”)

And here’s the thing to ponder, as Stearns and the sport’s other 29 owners commence with burning the midnight oil the next few nights in Nashville, Tenn., at the winter meetings. It would be both prudent and patient for Stearns to keep strengthening the core of his roster and his minor league system, something that started at the trade deadline two months before he was hired, something that will go a long way toward allowing the Mets to catch up with the Braves and the Phillies, for starters. Cohen is paying him for his acumen, after all.

But the notion of New York being different than Milwaukee isn’t just an abstract truth. It’s real. And baseball remains a sport without a salary cap. You can make a logical argument against acquiring anyone who’ll cost a small fortune — after a while the Wilpons turned that into an annual rite every bit as reliable as the tree lighting in Rockefeller Center.

Maybe last year proved you can’t win simply by spending money.

But spending money is still one of the privileges of baseball — the last of the sports without a cap — and one of the expectations when you operate a team in New York. Maybe it’ll work out, taking a flier on Luis Severino. Maybe Joey Wendle will be a terrific addition to the Mets’ depth. But those have to be just the appetizers.

Cohen insists there will be a competitive product on the field at Citi Field next summer, even after initially hinting there might be a rebuild instead. He has insisted from Day 1 that he is just as committed to building something that will last, which is why he kept his porch light on for Stearns, who seems to buy what the boss is selling. It isn’t always easy to service both, to respect today while caring for tomorrow. Maybe in Milwaukee you can make a choice.

Not in New York. Here, in baseball, you need to do both. It’s not an easy gig. But, then, at $10 mil per, it really shouldn’t be.