Many experts, including my personal hero Paul Graham, strongly advise against founding a company on your own:
All investors, without exception, are more likely to fund you with a cofounder than without... If you don't have a cofounder, what should you do? Get one. It's more important than anything else.
Research on the subject appears to be mixed; browsing through abstracts, I would conclude that, all things equal, having a co-founder tends to be a benefit on average, but the effect is not as large as Paul Graham seems to imply. Informal sanity-checks confirm that many successful companies were single-founder:
plant viruses? Here's my speculation: perhaps we should differentiate the question of "should I get a co-founder" from "should I fund an entrepreneur who has no co-founder." Having a co-founder right away might be a "bozo filter" for an investor: it helps convince an early investor that you're not a bozo who nobody sane will work with. However, if you are such a bozo, somehow getting a co-founder won't change that fact that you're a bozo; and conversely, if you're not bozish (bozonic?), deciding to initially forgo having a co-founder will not turn you into an innate bozo. Therefore, I speculate it may be vitally important for an investor to insist on co-founders, but it may be less important from the founder's point-of-view for a pre-funding founder to immediately acquire co-founders.
Further reading on the topic of founder team size:
- Chandler et al: Antecedents, moderators, and performance consequences of membership change in new venture teams
- Pasanen and Laukkanen: Team-managed growing SMEs: a distinct species?