Don't take this the wrong way, but your entire rationale for having co-founders seems to be based on fear and negativity. Your comment implies that you're most interested in providing yourself with the comfort that somebody else is taking risk too and will be there to drown with you when the ship sinks.
Per my other comment, this is simply the wrong reason to bring on a co-founder. If you truly aren't confident in the opportunity you've identified and don't feel comfortable owning your pursuit of it, convincing two or three other people to come along for the ride isn't going to prevent failure. In fact, it's probably only going to make the process of failing even more stressful.
It's not about fear of failing. I wouldn't do it again unless I was convinced the venture would be successful (and I think there's a significantly increased chance of that, based on what I learnt during the failed startup and since).
What I'm saying is that having equal co-founders gives you the ability to share the workload, emotional strain and get through the pain barrier.
It's obviously not impossible to build a huge business as a single co-founder, but it's unlikely that I'd want to do it again!
Per my other comment, this is simply the wrong reason to bring on a co-founder. If you truly aren't confident in the opportunity you've identified and don't feel comfortable owning your pursuit of it, convincing two or three other people to come along for the ride isn't going to prevent failure. In fact, it's probably only going to make the process of failing even more stressful.