[downandout]

This. A mediocre product with a strong marketing strategy can make millions. A spectacular product with no marketing plan will make nothing or close to it.

Products that spread through word of mouth are few and far between these days. Facebook has made sure of that by snuffing out most newsfeed virality (unless you are paying them for it) such that even if your customers want to share your products with their friends, few of them will see it. Growth rarely happens by accident these days.

Do not attempt to even create a product that you are going to depend on for your livelihood without a specific marketing strategy already planned out and ready to execute. That strategy should be able to generate a positive number when when you subtract estimated, realistic customer acquisition costs from their estimated, realistic lifetime value. There is a great podcast called TheTop [1] covering a number of tech verticals where existing companies go into these numbers in specific detail. I would recommend you find an episode about a company in your vertical and listen to their numbers.

[1] http://nathanlatka.com/podcast-thetop/