Everyone is faking it until they make it. I think a deciding event is when someone takes on no other employment for 1 year at a time and works 110% all in on their startup, then they are definitely an entrepreneur and have made the leap from the sidelines.
One idea I didn't see listed elsewhere: Try to go and work for an early stage startup if you are having trouble getting a startup off of the ground yourself. You will learn a lot more as one of the first 10 employees as you do as one of the first 10k. If you tell startups founders you eventually want to do your own startup they respect that and will try to give you opportunities and can share a lot with you about their startup experience.
Also hopefully if you are part of a successful startup exit you will get some street cred and some money to live off of. If it's a failed startup even better as you will learn even more from that experience.
One idea I didn't see listed elsewhere: Try to go and work for an early stage startup if you are having trouble getting a startup off of the ground yourself. You will learn a lot more as one of the first 10 employees as you do as one of the first 10k. If you tell startups founders you eventually want to do your own startup they respect that and will try to give you opportunities and can share a lot with you about their startup experience.
Also hopefully if you are part of a successful startup exit you will get some street cred and some money to live off of. If it's a failed startup even better as you will learn even more from that experience.