I had a unique idea that I implemented in my part time. The site was featured on Techcrunch a few years back and quickly started making a lot of money. Within a few months a handful of VC funded competitors sprung up. They were able to iterate on the concept very quickly and completely destroyed me within the year by developing a significantly better product then I did.

The moral of the story: Working on your startup part-time is a great way to mitigate risk while you build out your first version. However, if you see some traction quit you day-job and start executing relentlessly.

I think it would also be tricky to explain to your employers why you're working on a startup on the side.

Was your name featured on TechCrunch, or just a URL?

I've tried doing "anonymous" startups under pseudonyms, it's hard to be taken seriously by the likes of TechCrunch, etc.

That is sad - I sympathize with you. What was the idea and why couldnt you also get funding when it started making money?

I think it's almost always a mistake to hope you can get your startup off the ground while working part-time. Usually people will only do the extremely hard (and icky) work necessary when they're presented with a sink or swim scenario.

"...Most founders of failed startups don't quit their day jobs, and most founders of successful ones do. If startup failure were a disease, the CDC would be issuing bulletins warning people to avoid day jobs." -- The 18 Mistakes That Kill Startups

I disagree.

I'm onto my second startup. My first one is (just) profitable and my second is showing very promising signs.

I put all the profits back into my businesses, so I work three days a week to pay my personal bills (and temporary business expenses). Fortunately, my job lets me go in whenever I want, which helps me juggle my time.

I think it works pretty well. It's meant I've never had to take any outside investment and yes, working my day job gives me time to reflect and come up with new ideas. It undoubtedly makes me more productive.

Being able to go in whenever you want is a pretty key difference from most day jobs.

I currently have a job like that but it is not too much of an advantage. One still has to put in 40 hours of productivity and you get tired at the end of the day like any other.

You actually work a day job part-time and work on your startup full-time. That's the reverse, which seems a lot better to me. I still think the ideal situation is over-time on your startup alone.

It can also equally be difficult even if you work from home, but have output monitored.

I've worked in an office environment where people could easily get away with surfing the web 80% of the time, no big deal.

I've worked from home where Subversion checkins are monitored daily.

No checkin? Well what the heck are you doing from home then? =)

What if the part-time work is a McJob?