When I give talks on this subject, my first suggestion.

Only start a business around something you've been doing every day, for the last 10 years + will continue doing for the next 10 years, every day, with or without pay.

This level of drive means you'll have expertise far surpassing other people + you'll stick with your niche, independent of any external circumstance.

Sticking with any one niche/topic/activity for decades is the best determiner of success... because no competition can touch you...