The first thing to understand is if they're looking to be a venture funded startup. Not all startups plan to raise money. If they have in the past, then issues equity is very standard and they should bring it up - if they havent, you can ask.

If they aren't looking to raise capital, then having equity won't be that important so you should try to get fair market value for your skills unless you want to work with that company / team, then negotiate.

If they are offering equity, then read through this:
https://www.themuse.com/advice/getting-startup-equity-everything-you-need-to-know

Hope that helps.