In our family we like to assign chores to the children just because they live in the family and have to help out. However, we also make EXTRA jobs available for pay. This is important because children need to learn how to manage their money.
When they do earn money, it's important to teach correct principles about budgeting, but then let them choose for themselves. This is one area where it is pretty safe to let them make mistakes and learn from their experience.
Here is a link to a whole list of articles on teaching kids about money. There is also a great book called, "The Entitlement Trap" by Linda and Richard Eyre, which is really helpful to read when deciding how to teach kids about money.