Although you'll need to spend 100% of your time on your startup, at some point, you don't have to start that way. Just make sure that you do whatever you can to fully switch context when working at your job or on your startup. Trying to do both, switching back and forth during the day, will drive you crazy. So in short, yes it can be done.

BTW: if you haven't read it already, read "REWORK" by the guys from 37signals. They talk about this misconception.

Also, starting your startup this way is incredibly hard. But, if you are really serious, you'll find a way and all of the sudden you'll find yourself spending more time on your startup that at your job. Good luck.

awesome, thanks for the book name

To some extent, it depends on the context . Personally, I think you should give your startup 100%. I've had to make a similar decision before and chose that route for a few reasons:

1. for most startups, except with the exception of some lifestyle startups, it won't succeed if you give it 50%.

2. it matters to you, personally. leaving the comfort zone was, to me, a statement to myself that I'm committed to this and have no fallbacks. With this point, I was really influenced by that one HN post about how Alexandar the Great would burn the ships they used to go somewhere for war, basically to say "theres no retreat"

I've been down the same road albeit everyone is different and the general scenario you painted isn't enough for me to warrant giving any advice off hand. If you'd like to get in touch, my email is my username at da google famous email domain.

Just do it.

It's all case by case. If you think it will work, make it work.