Paypal, Google Checkout, etc. all have extensive documentation at their associated websites.
And what do companies usually charge for setting up a e-commerce website?
I don't know. How many leaves are there on a tree?
EDIT; To clarify; what you can get as someone who has no track record with e-commerce websites, or much else for that matter, compared to someone who has a proven ability to develop said website, is vastly different.Additionally, whenever you are dealing with private information your liability factor increases tremendously. That liability costs money.
Or dose Pay-pal have one that comes with the cart
Does Paypal have one what? A shipping fee? How would they know what to charge for shipping? Perhaps you should look at a few e-commerce websites and see how they do it. most places charge a separate shipping fee based on where the product is being shipped. That is calculated at purchase time.