Along time ago I read a fantasy book series, I do not remember much but the main character was a girl and when she had to pick her job she was going to be a fool or something because she had no talents but was actually a long forgotten job of being a guide (or something I do not remember exactly) and the village mayor or leader's son was supposed to be able to talk to trees but was able to talk to stones instead. And there was a job called Finder or something where people found people or things.
The Farwalker’s Quest
This sounds like The Farwalker’s Quest, by Joni Sensel.
The main character had was a girl with the "long-forgotten job of being a guide." Check. She’s a Farwalker, who used to carry news and so forth between villages.
When she told him, he mused, “There aren’t supposed to be any Farwalkers left. Storian told us in class that the whole trade died out.”
“But what did they do? I couldn’t remember that part.”
“They were guides,” Zeke replied. “Messengers, connectors. They carried news and ideas, helped people trade goods, and brought ’em together into new villages when no one could see.
There’s a profession called Finder. Check.
Men dug where the Finders suggested and hit water before lunchtime. That prompted talk of a hunt for sea pearls. Their success was frightening for someone like Ariel, who had never seen a Finder at work—or who didn’t want something found.
The village leader’s son could talk to stones instead of trees. Check.
“So are you going to be Ezekiel Stone-Singer now?” she asked.
“I don’t know. I guess so. Does it sound crazy?”
“Yes. I never heard of a Stone-Singer. Tree-singing is weird enough.”
It could also be So You Want to Be a Wizard, though it seems less likely.
The main character was a girl
Check. The main character is a girl named Nita Callahan.
The leader's son was supposed to talk to trees but can talk to stones instead.
Sort of check. Nita can talk to trees, and she meets a boy named Kit Rodriguez who can talk to stones. Each initially finds the other's ability odd.