Paypal buying code?

Hiya, I have recently been asked to create a little flash site for some friends.

They basically make their own designs that they put onto t-shirts and want people to be able to buy them on the site. I figured the easiest way to do this would be with a paypal link that they just pay towards the owners email with.

I have never done anything like this before so im not sure how to go about it…

Any help would be much appreciated,