How long will it take...

I am citizen now and like to apply PR for my parents since I am the only child.

Any friend can tell me
1. whether I should have my parents here in the States first to apply or apply now while they are in shanghai?
2. How long will it take? before it is approved, can my parents visit me here in the States?
3. Any benefit I can appply for my parents? especially health care benefits? they are 65 years old now.

Thanks a lot.