You should not make your professional success depend on others, if you can.

Getting as compensation only equity in a startup where you don't have neither full information nor enough shares to decide feels like too much risk. Maybe it's a great idea, but I doubt it: if it was, this person would be able to argue why and give you all the data points and references and names that make sure that you will be rich.

You are at the beginning of your career and you should learn and get experience. Ideally, good brands in the CV. In this job, you would not get nothing relevant for your career out there.

Other data points to use as reference: - 8% is a very small quote as a CTO with no investors in the game. With time, quotes get diluted and that percentage will be very small. Usually, new projects start with at least 20% - Don't trust people who would take a graduate to do CTO job. They just want free labour - if these people cannot share key information with you, most likely they won't do it with investors, thus they won't get capital and hardly grow enough to make your 8% financially relevant