Having a prototype makes everything easier, including finding partners. Build your prototype, and then while you're out socializing with other startup founders, and/or beating the bushes for customers, investors, business development opportunities, and press, you can also mention "I'm also looking for another developer to join the company in a partnership role". Somebody will know somebody, and if you're selling the dream effectively they'll be inclined to make that introduction.<p>The problem with people looking for business partners is often that they imagine that an idea is enough to persuade someone to get involved. It rarely is. An existing friendship might be enough, but a stranger with a new idea (and nothing else) is just annoying. So, building a prototype proves you're dedicated enough to put some of your own skin in the game before asking anyone else to do so. That's a big win.<p>And, of course, there <i>have</i> been single-founder success stories. More than a few, in fact. So, if you never find a co-founder, if you can deliver a valuable product, you might still build a successful business. But it's obviously a harder row to hoe.