The payment terms section of your site should include:
- The payment methods you accept (Visa, Mastercard etc.)
- Missed/late payment conditions
- How you will handle refunds/returns
- How you will handle payment disputes
Because they are an intermediary between the buyer and seller, Etsy has very comprehensive T&C for its site. It establishes the rights and responsibilities of both the buyer and the seller. It also states that in agreeing to their T&C, the customer is also agreeing to the T&C of third-party services such as PayPal as well.