Remember that onboarding is an ongoing process, and it's essential to maintain open lines of communication, foster a positive culture, and provide continuous support to ensure the co-founder's successful integration into the startup.

Here is a condensed version, and it's important to adapt the checklist to suit the specific needs and circumstances of your startup.

1. Define the role and responsibilities.
2. Share the vision and mission of the startup.
3. Establish effective communication channels.
4. Provide access to critical information.
5. Introduce the co-founder to the team.
6. Assign mentors or advisors.
7. Set short-term and long-term goals.
8. Create an onboarding plan with a timeline.
9. Provide necessary resources and tools.
10. Foster a supportive work environment.
11. Clarify equity and compensation.
12. Monitor progress and provide feedback.
13. Cultivate a learning culture.
14. Celebrate milestones and achievements.

Other Resources:

Meeting Expectations Guide - complete one yourself, ask your cofounder to do the same