Payment question - do credit card transactions accumulate and process all at once?

I'm just working on the tail end of the design on a site I'm doing, so I haven't set up the payment options yet for our site. Having said that, I need to ask a question for my client that I don't have experience with yet.

He wanted to know if people pay by credit cart or other form of payment, are the sales totalled daily and then processed together? Or are they processed one at a time?

I think he wanted to know because of the fees associated with each transaction.

Is PayPal the best way to go?

You might look at our Recommended Services:
http://www.zen-cart.com/index.php?main_page=infopages&pages_id=27

Zen Cart does not "collect" the money ... you have to pick the Payment Modules that you wish to use such as:
Check/Money Order
PayPal
AuthorizeNet AIM

and then for some, such as AuthorizeNet AIM, you would need to setup an account to work with your bank and the processing company ...

The Recommended Services can help you in rates for these services and in helping you get something like AuthorizeNet AIM or another service to work with your business, or your client's business, to accept credit cards ...

And, yes, gateways like Authorize.net will collect all the payments made during the day, and deposit them to your bank account in daily batches. The actual time between collecting payment and arriving in your bank varies from service to service.