[muzani]

The market should already exist for most products. For the iPhone, the market was feature phone users who played Java apps. For a social media app, people should already have created these social groups elsewhere, and those groups would be straining from the poor technology. For SaaS, someone should already have hacked a solution together.

Personally I say figure out your initial market and even your marketing approach before you write any code at all. Get buyers lined up for the product before you build it, preferably with cash on hand, ready to pay you.

Validating a business model also means taking on tons of technical debt. Build your app with PowerPoint or Wix if you have to, just to prove the concept. Don't build the app too much until you have something people are willing to pay for. You'd be surprised how many SaaS are badly built at launch, including Stripe.