questions- from incoming freshman

I'm an incoming freshman and have a few questions about Greek life.

1. When does rush happen, fall, spring or both?
2. I have a (minor) health condition and it probably isn't a good idea for me to be drinking (I don't currently). Will I feel left out or awkward for not drinking? Will people try to pressure me to drink?
3. Is it normal for non-Greeks to show up at parties?
4. Do most people in Greek life have at least a few friends who aren't Greek?
5. What are costs typically like, including and not including housing?

I'm a girl if that matters.