Adding payment part of a new website that has yet to be built

Page 1 This would be what appears on our website under the Subscription button. It would also appear in our Media Kit in pdf format, with the links going back to the website. Page 2 This is the content that would appear on the website when the Subscribe On-Line button is clicked. The Shopping Cart (4 options) would only be used for credit card sales. From this page they could click here (for credit cards) to send us their information and be sent off to the payment site for credit card. OR, from this page they could click here (for on-line banking) so as we get sent their information and then they would go off to their bank's online system and make the payment to our account? Page 3 This is the sort of content that would appear on the website when the Subscribe By Post button is clicked. I imagine they can print it out from there, fill it in and post with their selected payment (cheque/credit card) option. Somewhere in amongst all this we need the ability to accept credit card payments for other stuff such as advertising, where they can enter a reference such as invoice number and nominate the amount being paid. Could also look here at adding a 2%-odd credit card fee. What we need to achieve here is simplicity and economy and all that goes with that.