We are a customized student travel company organizing multi-day tours for specific school groups, so our tours are not open for public sign up.  Rather, we give the teacher a private key or link to access their event page where people can register and sign up.  Because of the higher price of our tours, and the typical 9 mos between registration and actual travel, payments are made in installments – typically we charge a deposit, then the remaining balance is paid in 3 equal installments, all online.  We currently use Joomla and a customizable registration component that links to Authorize.net payment gateway, but we might be interested in switching to Word Press.  Please let me know if Rezgo can do the above, and how much / what percentage we'd be charged for the transactions.
Thanks.