What assurance can I have in case a startup fails?

I am a coder and have very little in-depth business knowledge. I was recently approached about joining a very promising startup with a great idea. Only problem is that they were unfunded and would need me to work for equity which i have never done before. So in a nutshell my question is this, as i am the technical person and really the only one that is investing a billable commodity, is there anything i can ask for in a contract that assures me some sort of return if the business never takes off or just dies? None of this is being done in bad faith and i have already asked them and they have agreed to me asking around for a situation that makes sense. Any ideas or suggestions would be appreciated.

In this situation it is very unlikely you are going to get anything if the business doesn't work out, you just need to make sure you are compensated enough for the gamble you are taking (ie. if the business succeeds and you end up getting paid what you would have in a normal company, that's not enough). Work out how much equity/reward makes the risk worthwhile to you and there you have your deal. If what you want is higher than they will give, then move on.

One thing you mentioned that is worth pointing out, technical skills aren't the only billable commodity, don't undervalue other peoples contributions because it's not coding, that will likely lead to conflict.