The company I currently work for started with zero marketing in the mid 2000s (2004/2005). We grew into a multi-million dollar company. We're in the home and garden e-commerce category.
We didn't really start doing any marketing until 2010 (Google TV, at that!). Now, though, competition is a mess (tiny sites rank above established brands) so we're almost forced to do some form of PPC. In some ways now, you're completely at the mercy of Google and their latest algorithm update, regardless of whether or not you follow the SEO rules.
To answer your question though, if competition is low it can definitely be done, just do everything with SEO in mind, but design and write for users.
We didn't really start doing any marketing until 2010 (Google TV, at that!). Now, though, competition is a mess (tiny sites rank above established brands) so we're almost forced to do some form of PPC. In some ways now, you're completely at the mercy of Google and their latest algorithm update, regardless of whether or not you follow the SEO rules.
To answer your question though, if competition is low it can definitely be done, just do everything with SEO in mind, but design and write for users.