I think the biggest risk is "death by fizzling out". Startups are fun... at first. Eventually, they hit a point where they (hopefully only briefly) aren't rem

I think the biggest risk is "death by fizzling out". Startups are fun... at first. Eventually, they hit a point where they (hopefully only briefly) aren't remotely fun and are instead hard freakin' work that you'd love to avoid. So spend some time engineering a "system" where you can't slack off (have a co-founder who depends on you and have recurring scheduled work days to avoid the "Meh, I'm pretty slammed this week-- I'll get back to things next week" state. The second biggest risk is failure to pull the trigger (or inability to do so). Know what your target is for jumping into it full-time (and make sure co-founders are on board with this target). Be sure you have the financial means to jump when the time comes-- start saving now. PROFIT generally comes a long time after REVENUE. I wrote a guest post on VentureHacks on this exact topic (http://venturehacks.com/articles/half-assed http://venturehacks.com/articles/half-assed ). As is often the case, some of the comments are really valuable.