In order to sell on the Diablo III Real-Money Auction House, you need a place to send the proceeds from your auctions.
Battle.net Balance with Battle.net Authenticator:
With a Battle.net balance, you can buy and sell items on the Real Money Auction House as well as purchase products and services on Battle.net.
PayPal with Battle.net SMS Protect:
You can send the proceeds from your Real Money Auction sale directly to a PayPal account linked to your Battle.net Account.
* PayPal is not supported in the following currencies: Argentine Peso, Chilean Peso, Brazilian Real, Russian Ruble