If you've truly lost faith in the founders and business -- which you have -- you should leave now & cut your losses. It's not going to work out, regardless of salary.
As for how to make money after you leave -- get a job or find consulting work. Then jump back into starting a business when you're ready again.
I'm starting a cloud company in Nairobi if you want to do something totally crazy ....
Talk to the people you meet and a new startup will come your way before that year's out.
Since you already are doing consulting on the side, i think you may be able to squeeze 3 months in on trying to get funding, just make every action Fast, Focused and Fundamental to your objectives. Godspeed!
If you're out of money it might be hard to pull this off as I've heard seeking funding is a full time job (or two, as your cofounders have shown) so the product has to be mostly good to go (for at least the time being) if that's going to work.
Using the product you already built with company funds is almost definitely off limits (IANL), so I'm not quite sure how that strategy could be feasible.
"I feel as though I've invested too much time and energy to bail now."
This is a very dangerous way to think about it. This is your life you're investing here.
Perhaps to break it down to oversimplified but still valuable math:
(probability of success)*(personal outcome) = expected outcome
If you think they have a 10% chance of succeeding, but if they do they'll be legitimately worth $10M of which you'll get 30%, then the expectation value is $300k.
Do that calculation based on the numbers that you personally feel are correct. Compare to what you'd be making doing something else. Take into account that you've already worked on it for a year and a half, which is probably at least worth $100k. More since you may never get it.
If the project can't even meet that minimal standard for being worth your time, then you're unlikely to even make what you deserve for your time, much less receive a reward commensurate with your risk.
[1]: http://www.lifehack.org/articles/communication/how-the-sunk-...
http://www.theatlantic.com/health/archive/2013/05/how-to-wal...
Eventually I did quit, and everything was okay.
If this is your second job ever, then it's natural that you feel like this job represents a huge portion of your life's work. That's only true in that it represents your life's work up to that point. When you are 60, this will be something you see as a tiny portion of your work life. Eventually when you list the things you are most technically proud of (which you said you are), this probably won't make the top 5, because you will make so many more awesome things over the course of your career.
Read 'Eric Ries - The Lean Startup'. Your time at this startup is not necessarily wasted, if you've learnt stuff, networked, and somehow helped you get your next job.
I'm currently reading through "What I wish I knew when I was 20" by Tina Seelig (more entrepreneur-y than expected, but pretty good) and this exact topic is discussed in Chapter 5.
> […] “even great ideas require a tremendous amount of work to reach a successful outcome, it’s incredibly hard to know when to keep pushing on a problem, hoping for a breakthrough, and when to walk away. We all know that persistence is to be admired, but when does it become foolish to continue working on something that’s never going to fly? Gil Penchina, CEO of Wikia, describes the dilemma wonderfully: “If you throw gasoline on a log, all you get is a wet log. But if you throw gasoline on a small flame, you get an inferno.” That is, it’s important to know whether you’re putting energy into something that has the potential to pay off. This is one of life’s biggest challenges. We often stay in dead-end situations way too long. This occurs when companies commit to a doomed product or project, or when individuals stay with jobs or in relationships that make them miserable, hoping the situation will improve. So how do you know when to quit? This is a huge philosophical question. It’s always a mammoth challenge to separate your desire to make something work from the reality of the probability that it will work. Of course, the more you put into a project, the more likely it is to succeed. But some efforts will never pan out, no matter how much time, money, or sweat is injected. The most scientific answer I’ve found is, listen to your gut and look at your alternatives. Essentially, you have to negotiate honestly with yourself. Do you have the fortitude to push through the problems in front of you to reach a successful outcome, or are you better off taking another path?
> So quitting is hard—but it’s even harder to do it well. I’ve seen people quit gracefully and others quit so clumsily that they leave a huge crater in their wake. As discussed in detail in chapter 8, you are likely to bump into the same people again and again in life, often in unexpected ways. This alone is reason enough to make sure that when you quit, you do so with careful thought about the consequences for those around you. Besides the impact that quitting gracefully might have on you later, it is just the right thing to do. You can never rationalize quitting in such a way that you hurt your colleagues, friends, or former business.
> A colleague told me about his assistant, who was doing a terrific job. He gave her great reviews and spent a lot of time talking with her about her career path within his group. She made it clear that ultimately she hoped to move into a different field, and my colleague was supportive of this. In fact, he told her he would be delighted to serve as a reference for her anytime. With this as a backdrop, my colleague couldn’t have been more surprised when his assistant came in one day and gave two weeks’ notice. The team was in the midst of a huge project, the deadline three weeks away. She was going to leave one week before the project was completed, putting the entire team in a very difficult position. My colleague asked her several times if she would consider staying one more week to help him get to the end of the project, which involved dozens of people directly and several thousands indirectly. She refused, saying, “I know you’re going to be unhappy that I’m leaving no matter when I go, so I decided to do what I want.”
> My colleague felt as though he’d been kicked in the stomach. It was nearly impossible to fill in the holes she left during the last week of the project, and everyone worked around the clock to try to fill the void. All those who worked with her will remember that decision. Despite the fact that she did a terrific job while she was with them, the damage she did to her reputation during the last weeks of her employment dwarfed all the positive things she had done in prior years. In sharp contrast, I’ve seen others quit jobs with remarkable style. Even if they were leaving because the job wasn’t a good match, the grace with which they left made such a positive impression that everyone involved would be pleased to give them a glowing recommendation at any time in the future. They provided enough notice to fill any gaps, they took the time to put their work in order so that someone else could pick up where they left off, and they even offered to help with the transition. These folks are heroes. They mastered the art of quitting well, and used their skill to turn a bad situation into something positive.
Source: been there, lots
Ignore the rest of the things you're worried about, don't say anything about serious doubts or that you think they are idiots, just let them know it's not a viable for you to continue to work without pay. Keep it simple.
If you're anything like me, this incredibly stressful time will end up materially pushing your career forward in the future.
I am pretty certain when you come back you would know much better what to do.
Be open and honest - just tell them that you need a salary. Going a year and a half with no salary is not something anybody has a right to expect from you unless you're already wealthy.
Tell them you need an actual salary and actual health insurance in the next 30 days. If the venture can pay you to keep at it, that's great. Otherwise you'll have to start looking around for a real job in a couple of weeks. Even the most brick-and-mortar type of businessperson will completely understand this.
Stick to your schedule. It will either work out or it won't.
If it doesn't, no hard feelings.