People hoping to make a quick buck by selling iPhones on eBay right after the highly anticipated devices go on sale Friday are going to be out of luck.

Apple on Thursday said customers buying the combination phone, multimedia player, and Web browser through one of its 164 retail stores in the U.S. will be limited to two on a first come, first served basis. The only other place where the phones can be purchased is through AT&T, which requires the buyer to sign up for a two-year service plan. AT&T is the exclusive wireless carrier for the iPhone in the United States.

If the initial demand for the iPhone is as big as expected, then the gadgets are likely to sell out quickly, which could make the hot items a lucrative piece of merchandise on eBay. Apple is apparently more interested in getting the $500 devices to as many customers as possible.

To assist buyers in using their new toy, Apple on Saturday plans to offer free workshops at its retail stores. In addition, the company said it would offer personal training through its One to One program. "Apple retail stores were created for this moment -- to let customers touch and experience a revolutionary new product," Ron Johnson, Apple's senior VP of retail, said in a statement.

Hype aside, the iPhone is considered unique because of, among other things, its multi-touch screen to control the device. The iPhone combines three products in one -- a mobile phone, widescreen iPod for playing music and watching video, and a Web-browsing device.

The iPhone is scheduled to go on sale in the United States at 6 p.m. local time Friday. Apple's online store will start taking orders at 6 p.m. Pacific time. The device comes in two models: a 4Gbyte version for $499, and an 8Gbyte model for $599. The AT&T service plan will cost from $60 to $100 a month.

People willing to endure hardship to be among the first to buy an iPhone started forming a line at 5 a.m. Monday outside Apple's flagship store on Fifth Avenue in New York. The high demand has led to others running online ads on Craigslist, offering to either hold a place in line for iPhone customers, or to buy the phones outright for people willing to pay for the service.