Affordable housing lotteries have exploded in popularity in the last two years.

Right now, The Sky, a luxury complex under construction at 605 W. 42nd St., offering 235 units at below market rents, is a hot ticket, and no wonder: A new Citi Habitats survey showed the vacancy rate in Manhattan is 1.07% -- the lowest in three years -- as the average Manhattan apartment rented for $3,475 a month.

Bob Kalin, a tenant organizer at Housing Conservation Coordinators in Hell's Kitchen, estimates there will be more than 100,000 applications for "the crumb" of "affordable" units offered until July 13, when The Sky lottery concludes.

The people seeking help at Housing Conservation Coordinators are not just applying for The Sky.

They're also trying to get into one of the 100% affordable projects the city subsidizes (five of those lotteries are on currently) and for ongoing lotteries in two other 421-a buildings in which 20% of the units will be available to low-income households via city lottery. (The Sky will have 1,174 apartments.)

Elderly tenants exhausted by treks to fifth-floor walk-ups tell Kalin they need a building with an elevator. Others are desperate to escape abusive landlords and heavy rent burdens. Old timers perceive winning the Sky lottery as their only chance to stay in Hell's Kitchen. Still others seek relief from overcrowded conditions, occasioned by the stratospheric rise in housing costs. "They are tired of living with six other people: They need a place of their own," Kalin explained.

HPD received 364,000 applications for 2,300 units offered in 26 lotteries in 2013. In August of that year, the Housing Connect website was launched, easing the application process and allowing people to fill out one profile online for use in multiple lotteries. By the end of 2014, about 1,500,000 applications were processed for 2,500 units offered in 41 different lotteries.

"I can't even describe it," Kalin said of the demand for an affordable home: "Everyone who walks in here needs an affordable apartment."

Mayor Bill de Blasio, facing epic resistance in Albany, has said the 421-a program -- which began in the 1970s to spur growth and gives developers massive tax breaks, sometimes in exchange for providing token numbers of affordable units -- should be junked if it can't be fixed. He wants to slash developer tax subsidies, double the number of mandated affordable units, and require developers to build affordable homes in all areas of the city. He also wants developers to keep affordable units at a low rent for 35 years as opposed to 20 or 25 years, and banish all tax incentives for the construction of condominiums.

The city has, indeed, been hemmoraghing affordable homes as luxury towers continue to pierce the skyline: More than 50,000 rent regulated units have been lost in the last three years, most to "vacancy deregulation." As of last night, no deal yet had been struck to renew the rent control laws or 421-a program although both were due to expire today. The elimination of what some perceive as residential segregation -- "poor doors" -- is also on the mayor's wish list.

The Sky has its own two-tiered twist, with lottery winners required to pay fees (how much is not yet known, though a discount is thought to be in the works) for amenities such as a putting green, water club and fitness center.

Who cares, shrugged Michael Reese, 33, a security specialist in Manhattan getting a degree at John Jay College who said this lottery would be his first. "I'd rather pay a couple hundred extra to use a pool than a couple thousand more for an apartment," he said.

Extra fees "don't matter," said the Iraq War veteran, adding that he simply wanted a better and more convenient place to live than Jersey City.

Reese faces especially daunting odds as he's not a neighborhood resident or member of a group receiving special consideration. Half the low-income units at The Sky are designated for people already living in Manhattan Community Board 4; 5% will go to people with mobility impairments; 2% will go to those with visual or hearing impairments; and another 5% are designated for municipal employees. And while non-NYC residents are free to apply, they are considered "only after NYC residents," said an HPD spokesman.

Kevin McLaughlin, 57, who is often in Hell's Kitchen to visit his mother, would love to apply, but he receives only about $12,000 a year in disability checks.

"I'm living in a church, uptown in the Bronx," he sighed.

The housing squeeze, he said, "is getting worse. There's a lot of older people who need help." He planned on crunching numbers to see if he and his mother could apply for a two-bedroom, together. Perhaps her residency would give them an edge, he said. "I can't live with her because she's in a one-bedroom: And they just raised her rent," he said.

Applicants who fail to fall in the frustratingly exact "sweet spot" of income and circumstance have zero chance of even being considered for an interview, a prerequesite to determine their suitability as tenants, even if plucked out by a computer.

Individuals vying for one of The Sky's 70 studios costing $868 a month, for example, must make between $31,132 to $36,300 a year. A single person looking to rent one of the 120 one-bedrooms costing $931 a month can earn up to that maximum, but the minimum household income is $33,326.

A family of four people competing for one of the 45 two-bedrooms can make no less than $39,978 and no more than $51,780 a year, and so on. People earning outside the stringent income guidelines are often frustrated to discover they are ineligible. . City Councilman Mark Levine introduced a bill in April to create a task force to review the system to "make recommendations for improvements."

Meanwhile, "we don't play the lottery, but we will play this one," said Dan H. Dumitru, a retiree and cancer survivor who was recently inspecting the building's progress, pronouncing the development "very nice." His 35-year-old son, a registrar in an emergency room, had moved back in with Dumitru and his wife after a divorce and would be applying for a two-bedroom on behalf of them all: "He's the only one with an income," Dumitru explained. While the family was living in a two-bedroom apartment in the Murray Hill area, they would lose their home next year said Dumitru, who declined to explain why. "We have to look forward to next year: We need a new apartment," he said.