I sell software products I develop. Like another commenter wrote, you end up building what the market needs and not necessarily what you find interesting. It's

I sell software products I develop. Like another commenter wrote, you end up building what the market needs and not necessarily what you find interesting. It's also tough mentally, you could wake up and your revenue is cut in half, a new competitor appears, your software can become obsolete, etc. Having all this in mind, it's very fun and I love it.