If you'd like to add someone to your channels and groups for free, you can whitelist him and then send him an invite link.
Whitelisted users will never be kicked from your members-only channels and groups (even if they don't have active payments or subscriptions).
To whitelist a user, open your membership bot and send /whitelist XXX, where XXX is the Telegram user id number. If you don't know the user's id number, you can find it in the Users list on your Dashboard (Project > Dashboard > Users).
You'll then need to reply to the confirmation that your membership bot asks for. If entered correctly, your membership bot will give you the confirmation, saying "Done! XXX was added to the whitelist successfully."
Once whitelisted, the user won't be added to the group/channel automatically; you still need to manually add them in with the "Add member" button in your group or channel.
If the user has a previous subscription or Access Code, they'll still need to be manually added or the bot will still remove them at the end of their subscription period.
To remove that user from the white list, simply use /unwhitelist XXX.
NB! If you're unable to add a newly whitelisted user to your group or channel, be sure to have the user check their Privacy and Security settings. If they have Groups and Channels set to anything other than “Everybody,” they will not be able to be added to a group or channel by any means until that setting is changed.