Unfortunately, if you genuinely want to build something cool, the correct path is build it as open source project while having a job. If you want to make money

Unfortunately, if you genuinely want to build something cool, the correct path is build it as open source project while having a job. If you want to make money (at least break even the opportunity cost of a programmer), you need to work backwards: build things that you will be comfortable to pitch to your connections. Selling home-made chilli sauce to friends&relatives is unironically a better business model than building an app for most people.