Is there a way to take paypal info on the registration page?

Hi all,

I want to start of by saying that the support here has been amazing. I have a question about prosites. I have it installed in my multi site. I want my users to pay me a monthly subscription to have sites under my main site. I set up pro sites in the following way:

1. I give them 30 days free
2. I enabled the "pay to blog" feature which will shut the front and back ends down if they dont pay

So eventhough I am not taking their payment right away (since Im giving them the first 30 days free), I do want them to input their paypal info when registering for their site (on the registration page), so when the 30 days are up, they get automatically charged, and then charged monthly after that. I can't seem to find a way to this. Any help would greatly be appreciated.