Classes and workshops can be conducted in your Hackerspace (or outside of it) by members of your Hackerspace or by teachers and educators from outside your community. Not everyone charges for classes; sometimes they charge for the tools and materials needed, or sometimes Hackerspaces will charge for a seat in the class when a student brings their own tools and materials.
Take a look at how other Hackerspaces charge for different classes and workshops before you proceed. You can charge in advance (many Hackerspaces use Eventbrite, which includes payment processing) and at the door at the time of the event. Prices are usually set higher at the door right at event time, incentivizing students to sign up in advance for a cheaper deal on your class.
High quality teachers enhance the chances of drawing new people into your Hackerspace who may become members. Typically, teachers and Hackerspaces split the profits from the classes, with terms and contract agreed upon in advance.
Calendaring all of your financial plans - and event plans, and space rental plans - is not just a good idea, it's necessary. You'll need a calendar system that all members can access, such as a client or web interface.
Many Hackerspaces use GCal, especially because it is very versatile and can be adjusted for both private and public viewing, reminders can be sent via text or email, and has a lot of other tie-ins with many services lots of people use.