MARIAH'S MAXIMUM SPENDING EXPOSED!

Why she’s leveragin luxury rea estate

SPENDTHRIFT Mariah Carey’s shopping habit is so out of control, she’s racked up $18 million in mortgage debt on her luxe Manhattan pad!

Sources tell GLOBE they suspect the diva, 55, is using the borrowed dough to finance her $1 million-amonth shopping habit, which includes blowing “obscene” amounts on clothing, champagne and gifts.

Insiders dish she treats the whopping $3 million a year she pulls in on her 1994 holiday hit All I Want for Christmas Is You like mad money, squandering it as fast as she can on “obscenely expensive” designer duds and a supersized staff, which includes a worker assigned to fan her while she gets her hair and makeup done.