Making a living from building and selling apps is bloody hard work. Most apps fail to make a return on the cost of development, let alone sustain a lifestyle. The chance of failure is very high and the odds stacked against you. If you followed your passion and your app does fail, at least you’ll have shipped something that you can be proud of.
Building an app or even something is fun but to make it even more meaningful, it would be great if someone uses it. It would be even better if someone pays for it. For that to happen, we need to let people know of our service and that is through marketing.