hasn't made that much money but allowed me to get paid more at work and tipped our income over the edge so we could get a mortgage on our first house which was nice :) great decision and learning experience building products from the ground up and exciting/grounding interacting with customers who always like to push the limits of your product :)
I have noticed others who have a lot of job experience coding but not the business/product experience can find it difficult to prioritise things from a users point of view and or build reusable/extendable systems by anticipating how things are going to change in future.
Even if it fails terribly i think its a good learning experience and can work out in your favour... Word Smashing made some money from ads but $0 from listing on the android app store :D -$20 on app store ads actually...