In Harry Potter with the recent question (How much do wands cost?), we know how much a wand costs which is 7 gold galleons. What if the young wizard family can't afford that? Like the Weasleys were always poor, that seems like a big push for them to be able to afford that much for each child's wand.
They’d likely get a secondhand wand.
Though it’s not what most wizards would consider optimal, and it wouldn’t be quite as good to cast spells with as a new wand that chose them, wizards who can’t afford to buy a wand that chose them could buy or otherwise get a secondhand wand instead.
“Most witches and wizards prefer a wand that has “chosen” them to any kind of secondhand wand, precisely because the latter is likely to have learned habits from its previous owner that might not be compatible with the new user’s style of magic.”
- The Tales of Beedle the Bard
Hogwarts students are required to have a wand, but they’re not required to have a new wand. Instead of a wand that chose him, Ron got Charlie’s old wand, so the Weasleys didn’t have to buy him a new one.
“You never get anything new, either, with five brothers. I’ve got Bill’s old robes, Charlie’s old wand and Percy’s old rat.”
- Harry Potter and the Philosopher's Stone, Chapter 6 (The Journey from Platform Nine and Three-Quarters)
Neville had his father’s wand when he was going to Hogwarts.
“Neville kicked aside the broken fragments of his own wand as they walked slowly towards the door. ‘My gran’s going do kill be,’ said Neville thickly, blood spattering from his nose as he spoke, ‘dat was by dad’s old wand.”
- Harry Potter and the Order of the Phoenix, Chapter 35 (Beyond the Veil)
Hogwarts students don’t have to buy new wands.
Hogwarts covers the cost for those who can't afford the necessary school supplies. From Harry Potter and the Half-Blood Prince Chapter 12 Silver and Opals Dumbledore's first meeting with Tom Riddle.
“Yes, sir,” said Riddle again. It was impossible to tell what he was thinking; his face remained quite blank as he put the little cache of stolen objects back into the cardboard box. When he had finished, he turned to Dumbledore and said baldly, “I haven’t got any money.”
“That is easily remedied,” said Dumbledore, drawing a leather money-pouch from his pocket. “There is a fund at Hogwarts for those who require assistance to buy books and robes.