It's never too late to start.
Trust me, I just joined this year: I'm a junior.
It's a no-cut team.
During practices, it varies depending on your coach, your team and your own personal abilities. Day before races are shorter practices. On hard days, girls ran about eight miles. Boys ran at least ten. On medium days, we run for a certain amount of time. Generally around forty minutes straight. If we do timed hard days, we go for an hour. Races themselves are generally 3.1 miles. I hear there're shorter races, but we only ran one 2 mile race and that wasn't even official.
Mile times also vary. Some people actually do average on miles, but can keep it consistent so they get a better 3 mile time than those that can run the mile faster than them. It's all on endurance. But to give you an idea:
Our fastest girl, her mile time was under 5, I'm pretty sure. Her 3.1 mile time was 18:06. She won districts and is going to state.
Our fastest guy, I have no idea what his mile is, but I can guarantee it's probably got 4:30 beat xD His 3.1 mile time was 16:03.
That's what you see on varsity. For JV: most girls I've seen get around 21-25 minutes in their races depending on the course, since hills or certain types of terrain take different amounts of time for people. And the average mile I've heard or seen is around 6:40-7:30 minutes.
You don't have to be in shape at all. There was a girl that joined and she'd been running only a mile or two a few times a week during the summer because she was lazy. She came and nearly died and wanted to quit. Her first race she got a time of 38:45. She didn't even show up to all of the practices, and she always gave up at some point in the first few weeks during practice, but by the end of the season she got her time down to 30:51. That's massive. So you don't have to be in shape. You just have to be determined to keep going and commit to it.
But it'll be helpful to be in shape or at least be used to running a few miles. So running a few miles a few times a week would definitely help you.