GAZA CITY -- WHEN Mohammed Sawiri was rich, he bought his lover a cellphone so they could secretly text. He was a “tunnel millionaire,” one of the thousands of Palestinians who became wealthy overnight, by Gaza standards, earning $18 a day hauling goods through one of the hundreds of passageways under the border between Gaza and Egypt.

The high school dropout was 17 when he began working in a tunnel. Now, at 23, Mr. Sawiri sells 25-cent cups of tea, Turkish coffee and Nescafé in a Gaza park, facing an ice cream shop where he once ate $1.25 vanilla ices. On a good day, he makes $5, and instead of texting his lover, he slips her letters.

“I used to choose the most expensive places,” Mr. Sawiri said, sighing, from his tea stand in the Unknown Soldier Park — named for a statue commemorating Palestinian fighters that was torn down nine years ago by Islamists. “You pimps, I used to eat in your place,” he added, addressing the ice cream shop on an overcast day. “Now you mock me because I am a tea seller.”

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Mr. Sawiri’s nephew, Muhanad Saharna, 13, is his “waiter,” and helps hustle for customers in the Unknown Soldier Park. Credit Wissam Nassar for The New York Times

Mr. Sawiri is among the thousands of men thrown out of work last year as Egypt cracked down on the tunnels, accusing Gaza’s Islamist Hamas rulers of offering safe passage to militants fleeing Egypt. The men swelled the idle work force in Gaza, where unemployment has soared to 44 percent since last summer’s war with Israel.

The tunnels brought in just about every imaginable sort of merchandise — live cows, zoo animals, cars, soda and cement. They flourished after Israel and Egypt tightened restrictions on trade and movement in 2007, to punish Hamas for seizing power in Gaza.

Some former tunnel men have become vendors in this park, including Mr. Sawiri, who borrowed $65 from his mother to set up his stand in a tree-lined corner. A rare open green space in Gaza, the park is a central gathering point. Rallies typically begin here, and during the war, hundreds of people made homeless camped in the park. It attracts rich and poor, idle men and pram-pushing moms, students and lovers, making business lucrative.

Mr. Sawiri’s nephew Muhanad Saharna, 13, is his “waiter,” hustling for customers, and is paid about 75 cents for every 10 drinks. Sometimes, Muhanad charges extra and pockets the difference.

MR. SAWIRI’S best customer is an elderly man nicknamed Abu Basel, nattily attired in a suit and beret, who sits on a nearby bench.

A waiter for another tea stand flirts with women, gets their phone numbers and sells them to Abu Basel for $2.50 each, Mr. Sawiri said.

Either way, Abu Basel is a lonely heart magnet.

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On a recent day, a woman sat on a bench facing Abu Basel, striking up a conversation. She said her polygamist husband married a younger woman and now ignored her. “He only washes when he’s going to sleep with her,” she complained, her voice drifting over.

Abu Basel ordered two Turkish coffees, one for the woman. Muhanad rushed over with them; the woman complained that they were not hot enough.

Nearby, two bearded, deeply conservative Muslim college students sat on a low wall, discussing upcoming exams, their eyes cast down so they would not accidentally commit a sin by looking at the women. A little farther away, Mohammad al-Ghoul, 6, his front teeth missing, tried to sell newspapers for 25 cents apiece.

“I’m helping my brother,” he proudly lisped, staring at his sibling, Abdul-Rahman, 13, in adoration.

A born chatterbox, Mohammad gaily told of how he had started a fire in their home last winter by knocking over a candle, and of how his brother had come to his rescue. Many Palestinians rely on candles for light because of hourslong power cuts, made even worse by Israel’s bombing of the local power station last summer.

“Want a newspaper?” he asked, without missing a beat.

Three women strolled to a bench near Mr. Sawiri. They were probably from Rafah, a town on the Egyptian border in south Gaza, he said, looking them up and down.

Compared with Rafah, “this is Paris for them,” he said. “There are no parks in Rafah, and women can’t stay outside like this. They stay here as long as they can, and flirt.”

A man in a tight shirt sauntered over, striking up a conversation with one of the women, who was wearing a peach head scarf and matching long robe, a gold belt accentuating her figure. An hour later, he pulled out his red cellphone, appeared to punch in a number and walked away.

A couple strolled to another bench. The woman, in head-to-toe black, shyly lifted the man’s hand, sniffing it, as if for perfume. She let his hand linger in hers.

A skinny man selling cigarettes asked Mr. Sawiri if he could have some water. Mr. Sawiri pays a nearby shop 25 cents a day to fill his jerrycan — the tap water is too polluted to drink. Muhanad scrambled to pour him a cup. “May God reward you,” the cigarette seller said.

Three girls in school uniforms bought yellow ices from another peddler. One of them, Myasar, 14, said they were temporarily attending a school near the park, as their own was being used as a shelter by Palestinians still homeless from the war. A smiley-face badge was pinned to Myasar’s uniform. She pointed to it. “Smile, you are in Gaza!” she said brightly in English.

A 15-year-old beggar slowly walked around the park, trailed by her younger sisters, 13 and 9, their faces, torn clothes and bare feet smudged with dirt, their toenails painted pink. Their names are being withheld for their safety.

The older sister approached Mr. Sawiri, shouted that she was in a bad mood, then climbed an advertising billboard near his tea stand. “Go away,” he yelled.

“I can do what I like!” she shouted.

With her hands on her hips, she later said some of the men in the park were calling her “bad names,” setting off her bad mood.

“Why would I do this if I didn’t need to?” she said. “My father is blind, and my mother is sick.”

“And she’s pregnant again,” said the younger sister, sighing.

Mr. Sawiri whispered that the 15-year-old moonlighted as a $5 prostitute.

“Israel should just pour gas on all of Gaza and burn us,” he said. “Nobody should live here.”

WHEN Mr. Sawiri lost his tunnel job in February 2013, he sold his motorbike for $1,600, his smartphone for $130 and his computer for $140. He could no longer support his sister Samia, 34, a single mother with seven children. She began making and selling soap from her apartment in Gaza. She married off her teenage daughter, and four of her sons work in the park, including Muhanad.

Mr. Sawiri moved back in with his mother. Once a week, he pays 50 cents to check his Facebook page at an Internet cafe. Children on his lover’s street tell him when her husband is away and pass on his letters.

Mr. Sawiri fell in love when he was 16, when his lover beckoned to him from her doorway, giving him money to buy her candy. Her hand lingered in his. “Why did God create us with hearts? To love, right?” he said, tapping his chest. “My heart found its love; it will never change.”

His lover cannot get a divorce — she has no grounds to convince a judge in Gaza’s Islamic courts.

As he spoke, a man on crutches wobbled past. Muhanad leapt up. “Want a coffee?” he asked.

“Give me a cappuccino,” joked Rashad Abu Ghanayem, 25, an unemployed theater writer injured in a motorbike accident. He then ordered a coffee.

Muhanad charged him double.

Correction: June 13, 2015

An earlier version of this article misstated the year that Israel and Egypt tightened restrictions on trade and movement in Gaza to punish Hamas for seizing power. It was 2007, not 2006. (Restrictions had also been tightened in 2006, but that followed Hamas’ rise to power in democratic elections, not its ouster of its rival, the Fatah party, which took place in 2007.)

A version of this article appears in print on June 13, 2015, on page A8 of the New York edition with the headline: A Gaza ‘Tunnel Millionaire’ Falls on Hard Times . Order Reprints| Today's Paper|Subscribe