admin approval for new user (auction theme)

I would like to request something similar within this topic.

I like to allow and disallow users to have a ability to bid, in other word i like to set each user role/capability of bidding.

Lastly I want to only allow user registration by invitation only? is this possible? or have some sort of approval for each user registration where in as they dont get instant access to website without admin approval.

I hope i made it clear here.

thank you