Always ask about the preference stack. You'll rarely discover anything interesting, but if you do, it'll completely change how you value your equity grant.
https://angel.co/blog/liquidation-preference-your-equity-cou...
https://angel.co/blog/liquidation-preference-your-equity-cou...
"How much would the company need to sell for before my equity has value?"
Key #2 (not mentioned ANYWHERE): "Can you guarantee that my equity will always be worth at least that in case of acquisition for the above value?"
Key #2 stated in writing (congruent with typical verbal promises of implied future wealth) will actually protect you and possibly justify your salary sacrifices.
Without Key #2 guarantees - the next round of funding will likely push your equity value out of existence.