Rob is basically correct.
It's 20 for a regular membership. That entitles you to all rights and privilages including voting on amendments and at election time.
You can buy extra membership cards for use by immediate family at 5.00 per card. The extra cards comes with all rights and privilages except voting.
If your wife wants to be able to vote she would need to purchase her own 20 regular membership.
If voting for her is not an issue then the 5.00 extra card is all she would need.
So I think basically you are probably looking at 25.00 and would be issued two cards but only one card can vote.
Did that clear it up or make it more confussing.
encouraging Nano's to go where no tank has gone before !!