June 12 seems to be the latest launch date by Blizzard for the Diablo 3 real-money auction house. It was originally supposed to be available by May 22, however the realities of online gaming got in the way.
The auction house will let players buy and sell weapons, armor, and other items in the game. According to Battle.net, Blizzard will retain $1 from each weapon or piece of armor successfully sold, and take charges a 15% transactional fee on commodities like gold or crafting materials. If auction house users choose to use a third-party service such as PayPal, an additional 15% will apply.
If players opt to use their Battle.net account, the 15% charge won't apply, but you will only be able to use money stored there for Blizzard games, subscriptions, and merchandise.