(Bloomberg Businessweek) -- Covid-19 is pushing New York City's affordable housing crisis to a breaking point.

Look at 25-year-old Jessica Lee and her husband, who needed four roommates to afford their $4,000-a-month four-bedroom apartment in Brooklyn's hip Bedford-Stuyvesant neighborhood, a relative bargain in the Big Apple. Now her husband and everyone else in the house have all lost their restaurant jobs and she's the only one still working—at a company making hand sanitizer. The landlord is threatening legal action to collect the $20,000 in back rent. "Nobody is hiring in the food industry," she says. "I'm on the hook, because I am the only employed person on the lease."

Two-thirds of New Yorkers rent their homes, making it America's biggest rental market, and it's always had its own crazy kind of housing math. But with unemployment soaring and the typical rent about twice the national average, the numbers no longer add up. A quarter of the city's apartment renters haven't paid since March, according to the Community Housing Improvement Program (CHIP), a group that represents mostly landlords of rent-stabilized buildings.