If you only work for equity, you're taking a lot of risk on yourself, see if you can balance equity with cash.
If you're only doing equity, the founders might be using you for free dev work - I've seen schemes where equity is given, but then the equity is in a third-party company (with a very similar name) that has no income and once the developers are done, they are stuck with worthless shares while the main company gets sold and founders get away without paying a cent in development.