1) Train dogs. (competition OB is their focus, they also do agility, tracking, etc on a smaller scale)
2) $100 a year. Generally speaking, at least with the one's I know/have been involved with, you pay to join, and so long as you work within their class schedules group OB is free or discounted. Some things are not free, but are discounted for members such as tracking, which is $80 for non-members, $50 for members, etc.
3) Like to think I'm getting something out of it. You get back what you put in, so if you want to do a lot of training, then a membership can certainly be worth it. If all you want is to take a puppy class or two, might just be better to pay for those and forgo joining.
They are forming a new agility club here in the next few months, and in all likelihood I will be joining that, as that is more my interest now. Fees are supposedly going to be $25 a year, with access to fields and equipment (sounds great to me!!).
GSDs- Mulder, Ridley, Vega
GSD on the half shell- Rigel