Basically you should make the same assumptions you would joining a project as a freelancer/contractor - if you make enough money and don't care about career dev

Basically you should make the same assumptions you would joining a project as a freelancer/contractor - if you make enough money and don't care about career development and job security and quite possibly difficult atmosphere then why not, a job is a job. But if you're joining with the assumption that you'll be able to develop your career, or that it will be a fun/friendly/familial environment, or that you're deferring making real money until you cash in your equity, it's extremely likely that you'll end up bitter and disappointed a few months/years later.