If he talks about "considering it" it doesn't sound like an clear YES.

But to put this aside - this risk is up to you - i believe the experience to get out of something stagnant and even move to a new place is worth the experience alone. Speaking for myself, i take every worthy experience i can get to push my horizon further and further.

I can only assume, if you do a good job and gain the necessary skills that you currently lack of, there is no reason he shouldn't consider you.

What happens in 6 months if you don't get the bump? Worst case you've improved your experience, got more runs on the board and can apply for another job, closer to the one you want.

I don't know your personal circumstances, but I would personally take the chance, if the new startup job is something you will honestly love doing for 6 months (or more), and you're ok with re-locating across the country for a period of your life. As I said, I'd do it, but I'm not you.

I would agree with shimms. It sounds like you're wrestling with security vs. opportunity. Sometimes jobs that provide that stimulation/opportunity fall into your lap, other times you have to take a leap of faith and see how it plays out. The decision becomes harder depending on your personal circumstances (e.g. family, etc.). But even then, people move across the country to pursue opportunity, even if it means uprooting your family. Just don't be fatalistic about it--i.e. if it doesn't work out, then all is lost. You will have learned new skills and something new about yourself that other people don't have the guts to pursue. Good luck!

I am fairly young and don't mind moving to a different state.

My next questions would be: What should I demand that will make him more obligated to keep his end of the bargain?

Is there a way that I could figure out whether the hiring manager is being genuine and not a used car salesman?

For what it's worth, I had a similar chance when I was younger and had no children and I passed it up. It is one of my deepest regrets. If you're young and flexible (no children, not married, no aging parents to care for etc) I'd go for it.

I am young and without any flexible. So moving is not really a problem. I wonder how can I make my case stronger or ask him to put down more on the table besides just "maybe".

How solid is the startup?

The startup is actually pretty good. They are selling real product and it has very positive reviews in market.

Are they profitable? Meaning, do you reason they will survive one more year?