21, you can do it from the States, there are many threads about it. Can be done in as quick as 2 months, 6-12 months is the norm if you are doing it full time. part time is 12-18 months, but again I know pople who have done it in 6-9 months part time.
You can start before you are 21, need to be 18 to start CPL, 18 for the IR, but 21 to be issued the ATPL