I've also done this and can agree with the parent of this comment. The problem here is once they have traction and funding, they likely have a full-time CTO. F

I've also done this and can agree with the parent of this comment. The problem here is once they have traction and funding, they likely have a full-time CTO. Fractional CTOs are generally needed at the seed stage when the technical solution hasn't really come together and they don't have this skill-set in house. They also don't have money. It's a slippery slope, and you're better off being a technical advisor (low effort, low equity, low risk) than working underpaid and overworked.