Anyone is eligible to join AOPA at any time. In fact student pilots
(regardless of point in time of training) can benefit thru many
of the training programs, e.g. Flight Training mag, the Mentor
program, the website. Plus the legal advisor option (an additional
fee) and the medical advisor (comes with AOPA membership).

No, I'm not paid by AOPA. Nor do I get any kickbacks (I wish!)