Both niches have potential, but I recommend starting with the business niche, especially since you have 12 years of experience in woodworking.
This gives you significant leverage, social proof, and credibility, making your PDF more appealing and easier to market. With your established knowledge and background, it will be more engaging and enjoyable for you to create content in this area.
Once you’re established and scaling, you could explore the mental health niche if it aligns with your interests and goals, as it also offers opportunities for impactful and meaningful content.