i'm in the process of setting up a website for a client which will be offering paid services (fitness related) through their website, and would like some advice on what would be the best, and possibly cheapest way (for the client) to do this in order to accept payments for different services. should i use a shopping cart based system? would they need some special certificate/license to accept credit cards? paypal or google checkout? i also need it to send some kind of a receipt to the customer which would give a very detailed description of what they're getting, how much it costs, etc. i've browsed around through different sites and found one that utilized paypal where it had a drop down menu where you could pick one option and then you could click pay now button, and it would allow you to pay for that. is the drop down menu something that's generated in paypal itself? also looking for some way to implement an agreement checkbox, so that when a user clicks the agree to terms checkbox, they can then press submit button to accept the terms of service, etc. sorry i'm being vague, because i'm still not 100% sure of how i'll be doing this myself.