The time commitment varies from chapter to chapter, but the first semester is the most time intensive as the new member goes through the chapter's New Member Education Program.
The time spent in this program will give you the opportunity to develop your leadership and time management skills, learn about the history of your organization, develop friendships with your new member class, as well as the rest of the chapter, and allow you to become involved with other organizations. After initiation into the chapter, expectations will vary.
Each chapter has weekly chapter meetings and other mandatory events (philanthropic, service, initiation, etc.) throughout the year both for the chapter and then Greek Life as a whole, but they are planned well in advance. The more you put into the chapter and the community the more you will get out of being a member.