You work with your dad because he wants you to be a merchant just like him and the only way to learn something is to actually do it.
Mom, why do I have to work with dad
First, a merchant is someone who buys goods and sells them to the public. Second, some merchants are rich enough to rule the town they in. The key is to buy for less and sell for more.
What does a merchant do and how much money does a merchant make?
Your father and the other merchants have to travel on rough roads. They even carry swords with them, because there are theives out there trying to steel the goods your father and other merchants had bought.
How do father and all the other merchants get the goods they sell?