It could be a plot for a movie: hand some Italian who made his fortune running a large modeling agency in Milan buys an $850,000 mansion on Maryland's Eastern Shore and surrounds himself with beautiful women, a limousine and horses.

Welcome to the world of Giorgio Piazzi, capo of a 314-acre estate on the Chesapeake Bay called Hinchingham, where every month some of the most beautiful young women on the East Coast come to train as models.

"Most of my models, I send them to Milan," says Piazzi, whose wooded enclave near Rock Hall, Md., is a basic training camp for tomorrow's cover girls. One week each month, Piazzi and a staff of photographers, wardrobe specialists and makeup artists rise with the sun and work with a half-dozen young models whom Piazzi has selected as worthy of his workshop. At the week's end, each model has a "book" featuring about 20 different photographs of herself, an asset it can take beginning models months to acquire.

If Piazzi thinks a model has the look of success, he sends her to Milan where, he says, she should earn about $60,000 her first year. Piazzi says he's sent to Italy 15 of the 25 women he's worked with since he started his workshop last October. His agency, called simply Fashion Model, pays the models' airfare, hotel and living expenses and also defers a $3,500 fee for the workshop until they earn enough money to repay Piazzi's investment. In return, the model signs a five-year contract promising to work exclusively for Piazzi.

"Otherwise I would have an army working against me," he says.

A big man with brown eyes and a basso profundo voice, 41-year-old Piazzi was a model himself as a teen-ager before becoming a waiter in London. His family tells the story of his early luck: One night, leaving work, he stopped at a London gaming club and turned $2.50 into $35,000 at the roulette and chemin de fer tables.

"That was my capital to go to live with a gypsy in Spain," recalls Piazzi. A couple of years later, in 1964, he began a modeling agency in Milan, using a telephone in a bar as his office. Today he owns one of Europe's largest agencies and is highly regarded in his industry, according to Jerry Ford of New York's giant Ford Agency. Twice divorced and the father of three sons, Piazzi visits Milan frequently but lives at Hinchingham with a blonde from Aspen who attended Piazzi's workshop but never left.

His second wife, Jan Stephens, is a former model who now runs a Washington modeling agency called Panache. She moved with Piazzi to the Eastern Shore three years ago after the couple had searched all over the world for someplace more secure than Italy to raise a family.

"Giorgio is charismatic, he believes in magic," says Stephens of her former husband's ability to spot faces that are destined to grace the world's fashion pages and billboards. "He has a good eye for talent."

Piazzi's eye looks for women between the ages of 17 and 25 who stand between 5 feet 7 inches and 5 feet 11 inches.

If chosen, a model is housed at Hinchingham (under armed guard at night) and is photographed on the grounds or in a large stable converted to photo studios. An on-premises lab provides prints promptly. Food and wine are on the house. For recreation there are horses and for transportation there's a limousine. For company there's a tame fawn named Bimba ("young girl" in Italian) who adds charm to the splendor of Giorgio Piazzi's private world.