HARLEM — Instead of paying rent on the first of the month, Antonia sends her landlord a bill.

“We tell them to take [my rent] out of the savings account,” the 39-year-old single mother joked.

Her “savings account” is the $14,500 the company that owns her building owes her after the state determined it had been overcharging her rent since 2008, when Antonia, whose full last name is being withheld because she is an undocumented immigrant, moved into the rent-stabilized two-bedroom apartment on Fredrick Douglass Boulevard, records show.

While the landlord has yet to pay her that amount, Antonia has not paid rent since December, sending the landlord a bill instead.

When she first moved in, she was told the apartment’s registered rent was $1,900 but her landlord, Emo Realty Partners, charged her a preferential rent of $1,600. Landlords will occasionally give tenants discounted rent, also known as preferential rent, that is lower than the rent registered with the state.

In 2010, after Antonia told the management company that she was having a hard time making ends meet, the landlord brought her monthly bill down to $1,400, she said.

“I thought, ‘Great, these guys must like me, they are really going to help me,’” she said in Spanish.

While her rent stayed around $1,400, the registered rent kept rising. In 2011, the landlord did not register the unit as rent-stabilized in an attempt to take it market rate, records show.

In 2013, Emo Realty told Antonia that the registered rent was $2,600, but they would allow her to pay $1,800 a month.

Once a rent-stabilized unit’s registered rent reaches $2,500 and the tenant moves out, the landlord can move to rent the apartment at market rate, according to state’s Division of Housing and Community Renewal.

When she found out about the increase to $1,800, Antonia was unable to afford it and thought she would end up in the street, she said.

But New York State Department of Homes and Community Renewal looked into the rent increase and they discovered that the preferential rent was more than the apartment’s legal rent, records show.

In 2008, for instance, the landlord registered the apartment at $1,900 when it should have been $1,448, records show. In 2013, the landlord said the registered rent was $2,600 when it really should’ve been $1,600 records show.

A representative from Emo Realty declined to speak about Antonia's case.

What happened to Antonia is not uncommon.

Landlords can use preferential rent to quietly turn stabilized units into market rate apartments, advocates say.

Tenants should be weary of landlords offering lower rents, Elsia Vasquez, the executive director of Pa’Lante a tenant advocacy group who helped Antonia through the process, said.

“Real estate is a business, no one is special,” she said. “Eventually the landlord’s kindness is going to go away. People who have preferential rent should take measures to make sure the legal rent of that apartment is accurate.”

Because she is undocumented, Antonia had a hard time finding legal aid. Some organizations told her they couldn’t help her because they receive federal funds, others told her they could only help if she was already in court, she said.

At one point Antonia visited a housing lawyer but ran out of the waiting room when she heard that the one-hour consultation would cost $300, she said.

Undocumented people are being exploited because of their legal status, Vasquez said.

“Landlords make these tenants feel that they are doing them a favor by letting them rent an apartment in the city,” she said. “Really, it doesn’t matter, in New York City there’s a ‘No Sweep’ law that means you can go around yelling ‘I’m undocumented’ and nothing can happen.”

Apart from awarding Antonia $14,500 in September 2014, DHCR's decision also made the apartment rent-stabilized again. For the Harlem single mom, that was the biggest victory.

Almost half the $14,500 are from treble damages, meaning the landlord willfully overcharged Antonia, according to the state.

“The money helps out a lot, but the biggest thing is not having the fear of moving out, the stress from not knowing what you are going to do tomorrow," she said.