Accountant Classic is a basic tool to track your monetary incoming and outgoings within WoW. It logs per-session and running totals of how much money you have spent and earned from vendors / loot / quests etc...

It also shows the monetary info in daily, weekly, monthly, and yearly view. You can also quickly to switch to show your other character's monetary information in each view.

Either click the minimap button, bind a key to accountant or use /acc to view your accountant log. The newly added floating money frame will also show the real-time money.