I started working on a bug tracker (who hasn't at some point, right? :)) because we were using Bugzilla at work and I absolutely hated it and didn't think it fit with our workflow at all.
About a year later I brought it to the team and we decided to switch to it. A few months of light iteration and polish after that and we launched it as it's own product (https://bugrocket.com) for $20/month.
Pretty happy with how it's going, too. It hasn't really interfered with the 'day job' at all besides the occasional email to answer or tweet to reply to. We have really flexible hours here so I shift my day around sometimes to accomodate both projects. Totally do-able.
edit: Seems there is some interest in the 'family situation' of these success stories. I'm married (with kittens, no kids) and it generally hasn't been too difficult to keep a balance. It's helped me a lot having some people working with me (especially on non-technical bits), and not just alone as a single founder. It's hard to say how much time I actually put in because it's kind of a 'here and there' whenever there's the opportunity kind of thing. I'd probably estimate 3-5 hours during the week and then either a lot (8+ hours) or nothing on the weekends, depending on else is happening.
About a year later I brought it to the team and we decided to switch to it. A few months of light iteration and polish after that and we launched it as it's own product (https://bugrocket.com) for $20/month.
Pretty happy with how it's going, too. It hasn't really interfered with the 'day job' at all besides the occasional email to answer or tweet to reply to. We have really flexible hours here so I shift my day around sometimes to accomodate both projects. Totally do-able.
edit: Seems there is some interest in the 'family situation' of these success stories. I'm married (with kittens, no kids) and it generally hasn't been too difficult to keep a balance. It's helped me a lot having some people working with me (especially on non-technical bits), and not just alone as a single founder. It's hard to say how much time I actually put in because it's kind of a 'here and there' whenever there's the opportunity kind of thing. I'd probably estimate 3-5 hours during the week and then either a lot (8+ hours) or nothing on the weekends, depending on else is happening.