One of the most interesting problems early-stage startups run into is when to actually invest in marketing. 

There's no one size fits all answer, but there are tested and true approaches. Most importantly, if you're a founder or early employee, the starting point is to assess where you are...

"We are working on an idea and have some early customers / users of our product"

"We have a company that’s making money (revenue positive) on a consistent basis, and has a clear business model and path to growth"

For early-stage startups, outsourcing marketing is almost always a mistake. This is because you haven't identified your market(s), and built enough of a community or customer base to withstand changes.

Rand Fishkin of MOZ, recently published a deck on all the ways startups suck at marketing, and how to avoid them. In some ways the conversation is similar to hiring a sales team before you're ready to scale: you have to actually do the work yourself first.

But the crucial point Rand makes, and that many people miss when they're busy encouraging you to outsource your marketing, is that marketing in a startup is a mix of strategic and tactical work.