Membership - Change Membership Steps

I have Membership setup on my site.

Currently, potential members are able to sign up for a membership and then have the option of buying through PayPal. Their membership is created whether they 'Buy' or not. They are sent their username and password via Wordpress. I don't want them to be able to create a membership account without buying the product.

Is there a way to change the steps of activation to first 'Buy' the product, then be redirected to register (create) their user account?