Payment on multisite signup with pro-sites and setup fee

Hi, As usual I have scoured the net and this forum for a way to do the wp-signup.php all in one hit creating a custom template such as in restaurantengine.com/signup. (This has been posted on here before and marked as resolved with no visible result I can see) I need to make an initial setup fee. I was thinking to do a paypal payment on registration for the website. And then do the usual upgrade in the account area in pro-sites. I do not want to douse my website in plugins as I have read you can just use the membership plugin and pro-sites plugin at the same time.
Thanks in advance for any help