Why is there a single Savings account?

In reality you may have more than one Savings account and separate accounts for Checking and Brokerage. To simplify the model and how it uses the Savings account, a single Savings account representing all of your Savings, Checking and Brokerage accounts. Within the model if there is a shortfall of income versus expenses, it will help balance using available Savings. When you add a purchase of a future home or vehicle, or even a One-time expense, this will also use your available Savings. Instead of adding the complexity of having to further select which account to use, a single Savings account was used in the final design. Since this represents after-tax income, all of these accounts can be used for cash.