Thanks guv1976 for your helpful response. I see this specific prepaid rate 1 day before pickup.
Its only saving me few bucks, but the risk of $150 no-show tells me not to go for it.
You're right - for cancellation before 24 hrs, the penalty is $50. Within the 24 hr window you cannot cancel, and will be hit with $150 if you're a no-show. I doubt if this will be enforced, so was looking for experiences.