If you're charging a subscription fee for your course you can include a FREE trial period.
A free trial period gives students full access to course content for a specified number of days before they are charged the first subscription payment. A credit card is required at the time of registration. However, if the student decides to cancel their subscription before the trial ends they won't be charged anything. Otherwise their subscription becomes active at the end of the trial and continues to bill on a recurring basis going forward.
When adding subscription based pricing check the box to include a FREE trial period and then choose the numbers of days in the trial.
You can include a FREE trial period with subscription based pricing.