Would you be less likely to ask someone out if you knew they'd never dated(and they were like 18)?

It doesn't matter to me, once is this first time.

I wouldn't hesitate if I knew the person well (as good or better than friends). and I knew that I would have a good relationship dating them.

everyone's gotta start somewhere. but make sure that your "everyone" is a good choice for a relationship based on their personality and not on their lack of a dating record.