I’ve done work as an advisor and fractional VP of Sales.
In my opinion, you should structure it as upfront cash compensation. This way you can reduce your risk exposure and increase your personal cashflow.
If you get enough gigs you will be able to replace your day job compensation and become a fractional CTO full-time. Happy to chat about it if you want to DM me
Who is your target customer and try to get in front of them as quickly as possible. If it truly provides value to them, they will be willing to provide feedback immediately.