Who’s got a billion to burn?

Well, Bill de Blasio for sure.

But also mayoral spouse Chirlane McCray, who has just been revealed as a world-class boondoggler in her own right.

Hey, the family that preys together stays together, right? And it’s only (your) money — even if it is quite a lot of it.

McCray is the proprietress of ThriveNYC, a mental-health-related something-or-other created four-plus years ago to give a little heft to the conceit that Bill and Chirlane were elected as co-mayors — which is nonsense on stilts.

That is, once upon a time, first spouses were content to pretend to be in charge of prettifying highways and things. It was honorable “work,” it didn’t cost very much and it filled up the spouse’s free time.

But this is 2019, and the general feeling — at least in the de Blasio administration — is that if there’s not a lot of dough attached to the spousal sinecure, it doesn’t really matter enough.

So, ipso presto, co-Mayor Bill coughed up enough cash to break a pack mule’s back and sent it off to co-Mayor Chirlane — who then went forth to cure Gotham’s mental-illness problems.

Fast-forward to Wednesday, when the City Council was startled to discover that McCray and Team Thrive are closing in on having spent an eye-popping $900 million since the program’s inception — and nobody seems to have a clue on what.

That is, nobody appears to have kept receipts; the subways and street corners are still overrun with crazy people, and nobody in charge knows what’s to happen next.

But let’s be clear: If your boondogglery sets the New York City Council back on its heels, you truly are soaring with the eagles.

Right up there with co-Mayor Bill, who started the week on his own sour note — announcing that his signature Renewal school program was closing up shop after pounding $773 million down a rathole.

Well, he didn’t actually say “rathole,” and the price tag has doubtless been lowballed — but he also had no credible explanation for the debacle, nor did he apologize for it.

“We did not say everything would be perfect,” burbled the co-mayor — as if anybody outside his immediate orbit expected an outcome even close to competent.

That’s because there never was any doubt what the program was about. That is, reversing Bloomberg administration plans to shut down 100 miserably malfunctioning schools, thus saving the jobs of barely competent teachers and administrators and shutting up small bands of noisy parents who loved the schools despite their failings. Think Stockholm syndrome, rolled into a big ball with the United Federation of Teachers.

But the co-mayor made performance promises when he initiated the Renewal program, few of which even remotely were met, and presently gravity prevailed: The program caved in on itself.

How many other big-bucks initiatives are in similar straits is unknowable — mostly because bureaucrats never blow the whistle on themselves and also because Gotham’s formal watchdog, city Comptroller Scott Stringer, is among the most incurious individuals ever to hold the office.

That the co-mayors could fly under the radar to burn through $1.6 billion to no obvious good effect is an embarrassment — but understandable in the abstract. Things happen.

That Stringer could sleep through it all is the real scandal; why does the city even have a comptroller, if that’s the standard of performance?

It is not, in the end, just about money. The programs at issue ostensibly are meant to assist particularly challenged people — the helpless, often homeless, mentally ill and small children whose futures are forfeited because they landed in shamefully nonfunctional schools, an experience from which they will never recover.

But there are other mysteries out there, too. Does anybody know how well — more likely, how poorly — the co-mayors’ hugely expensive pre-K program is working, especially that portion consigned to the city’s notoriously problematic not-for-profit sector?

How about the Hurricane Sandy recovery effort — six years, uncountable delays and billions of dollars later?

Has anybody even looked?

This principally is on the co-mayors, of course, but it is also on Stringer — who wants to be mayor, but who shrinks from demonstrating that he deserves the job.

That two such scandals should bubble to the surface unannounced is bad enough. That it should happen in a single week is worse — it’s an embarrassment.

New York is supposed to be better than that.

Bob McManus is a contributing editor of City Journal.