IMO, if you're savvy with your opportunity costs in your life (i.e., your time and whatever money you receive for it), you should never, ever accept ethereal long-term "gains" in lieu of immediate compensation. Your time investment is very real and concrete and spending it is irrevocable, and no matter how it's a "sure thing," equity in anything never is. There are far too many variables at play that you have zero control over. The founders could screw you over. You could get acqui-hired except you aren't part of the new team. The market conditions for your startup could turn out to be less than favorable. When it comes time to exercise your options, your shares could be heavily restricted and never be able to be sold or transferred. Investors could dilute the crap out of your shares to the point that you've actually lost money on the deal (which happens VERY often). Why waste a non-renewable resource like your life on something that very, very, very likely will yield you nothing?
More concretely, I would never accept a below market salary in exchange for equity in anything. I don't understand this practice. I will take equity as bonuses, perks, and so on, but I never factor it into my compensation considerations. Perhaps I'm at the place in life where risk doesn't attract me, but to me it's a foolish move even at 20 or whatever age it's apparently appropriate.
Take the real money and go buy lottery tickets. Your chance of success to become fabulously wealthy is about the same. Better yet, put it in a well-performing retirement account and guarantee yourself a bundle of money a little later in life. Why make yourself an underpaid, overworked slave for someone to make a few bucks when you could live a healthy, more comfortable life and have the same end game more reliably?
(And yes I know some people crave that sort of work environment, but I think those people are mentally ill ;))
I'm not saying you're a bad person if you prefer this situation or whatever. I just don't understand it, very likely never will understand, and at this point in life, have no interest in trying. :) I think there are a lot of people like me, though, who arrived at that conclusion the hard way by working their tails off for years and getting nothing in return, and then when it's over, looking back and seeing their mistakes in "taking the deal" so to speak.