Redirect to page after a somone signs up for an account?

What I want to do is make it so people can pay to register for 3 types of account when they go to the sign up page on my drupal site. I want them to be able to choose from two payed account and one free account and if they choose a payed account to be either redirected ( after sign up) to a paypal site where they can pay or use paypal right on the site ( somehow ).

I hope everyone understands what I mean.

Thanks.