If you want to invite someone for free or at a discount to join a paid Group, Course, or Bundle Plan, you first need to create a free version of the plan, which you can keep Hidden (so it's not publicly visible to other members). Here are the instructions for how to create a new plan.
Once you invite the member to the special plan, they will be able to access whatever it is this plan grants access to as long as they remain on this plan. Note: inviting to any hidden plan will follow very similar steps. You can use this article and video as a reference for inviting members at a discount (similar to Coupon codes) as well as inviting new members for free.
How to Invite Someone for Free
Once you've created a new free plan, you can decide if you want to keep this Hidden or make it Visible. Then, all you need to do is create a Share Link so that you can invite someone to join that plan for free.
Go to Network Settings > Get Paid > Plans and select the free plan. Under the Share Plan tab, you will see an option to create a Share Link for this plan.
Copy the new Share Link you created, and then send it to the person you want to invite in for free! They will not be prompted to enter a credit card or provide payment details when they join this plan.
This video will show you the steps for how to invite a member to join any plan for free: