We do not charge for our service – it's completely free from our end.
If you have an iPhone or Android, you can download the GroupMe app and not worry about text message charges. Learn how to download the GroupMe app.
Otherwise, the charges that may apply are those that you would normally pay for sending/receiving text messages, or for data if you're using the app.
Texts are charged as a normal US mobile number – so whatever you would pay to text someone in the US, it costs the same to text the group. Each text you send to a GroupMe number counts as one text to a mobile phone number – you are not sending five messages if your group has five members.
Some people who aren't on an unlimited plan may have a certain number of texts they can send and receive per month, so they should keep an eye on that count with their cell provider.