Focus on their personal well-being rather than external standards of success.
A happy NEET feels safe in their stagnation. They need to know that their value to you is not transactional. You love them for who they are, not what they produce. How to Raise a Happy NEET
One of the greatest risks for a NEET is the loss of circadian rhythm. Without school or work, days bleed into nights. Structure is the first casualty. Focus on their personal well-being rather than external