Depends on what your expectations are. I built https://www.delayed-tweets.com for myself and I'm a heavy user of it and I tinker with it when I have time (Heroku + Stripe, if you want to know). If it also becomes a source of income, so be it. Otherwise, it costs me just a little more than using an alternate service to do the same thing (like HootSuite, Buffer, etc). But, I get to tinker with it on the side, learning new things and making little improvements as I have time. So 6 months from now, I don't have to be disappointed that it didn't go anywhere. A side project is exactly that, something that you tinker with while you still have a day job.