When you are young is the time when you do startups - of course some would do when they are post 30/40/50 but you will find out it is more difficult to do this once you reach certain age (i.e. get married, have family etc.)
You need to have a goal in your mind - so lets assume you landed a nice job in Bay Area for 100k, lets say you would be getting a pay rise every year (or so) - but would you have to specialise in some narrow bit of tech to do that? Would you continue living like this for rest of your life? Getting pay rises every year (or so)?
From another point of view - when doing startup and specialising in some narrow tech does not sound like a good idea. You want to broaden your skillset, that is - not only tech but also doing business, growing your network of connections that may help you starting your own startup in the future. You need to try to get your head around all of the concepts you possibly can, learn lessons of this startup so you do not make mistakes in the future and do everything you can to get your brain producing ideas. At some point you will evaluate those ideas and most likely set up something on your own - and then you may end up being somebody like Richard Branson? Who knows!
My advice though, do not let your job to burn you out. Contribute more if you feel like it but do not go too far with it for 1) they will expect you to be like this 24/7 and 2) your health is something you can loose easily.
Long-ish piece of advice, so what about myself? I started as engineer in world-wide corp and after 8 years left to join startup. And I have done it 8 years too late since this startup is quite demanding and I'm handling all tech issues together with building the team and keeping them on track. So it's 10 times more challanging now than it would be 8 years ago (and I know it would, working 9-5 job is piece of cake).
Good luck and all the best!