Mr. Gerim is typical in another way: He does not think of Gaza as his home, but he has no idea what home is.

His grandmother, Haniya al-Kurdi, 80, was a little girl when her family left what is now Ashdod, Israel, in 1948. She has never been back, but has heard that there is a coffee shop next to where her home was. The closest anyone else in the family has gotten was in 2013, when Mr. Gerim’s sister, Sabreen, now 26, contracted cancer and was allowed to spend a year in Tel Aviv getting treatment. On the way there, her mother, Iktimal al-Gerim, asked their driver to point out Ashdod to them from the highway.

For Mr. Gerim, the family’s old property is an idea more than a place he can actually picture.

Israelis themselves he has had more experience with. When he was about 10, before the Israelis evacuated their Gaza settlements in 2005, Mr. Gerim climbed a tree outside his grandfather’s house to get a better look at the soldiers a few hundred yards away. Then he fell to the ground and broke his right hand.

He has been as enterprising, and as ill-starred, ever since.

He used to raise pigeons and chickens on his family’s roof, for fun and for food — until an Israeli airstrike hit a neighbor’s house and it collapsed on the coop, killing all of his birds.

He sometimes dreams of working in an automobile-manufacturing plant, of traveling overseas to learn how to build cars, then coming back to Gaza to make them. But the closest he has ever gotten is loading tuk-tuks — motorcycles with cargo beds — or handling a pushcart to distribute sacks of donated flour, sugar and other staples to his fellow refugees.

In the autumn, Mr. Gerim sometimes harvests olives. When there is construction work, he looks for chances to lay bricks or pour concrete. He has never had a regular job.

He is stoic for a 22-year-old, though this may be an acquired response to adversity: His father is mentally ill, Mr. Gerim says, given to flying into destructive rages over the slightest disappointments. His family — two younger brothers, their sister and their parents — all share a single room with a tile floor and blankets but no beds. The kitchen floor is sand. The family’s debts are choking them, he says.