Louis Foy, 21, sat in the lobby of the Madison Hotel yesterday, looking more like a well-heeled guest than a chauffeur. His employer's borrowed yellow Audi sat outside on 15th Street NW between two gigantic Cadillac limousines.

Foy, a senior at Columbia University in New York City, was earning money while in town: $225 plus tip for driving a wealthy executive to inaugural events for three days in Audi provided by the businessman.

"It's been fun," said Foy, whose parents live in Georgetown. "But I certainly wouldn't want to make a profession out of it."

Foy was not alone. Hundreds of amateurs were out hustling a buck this week and established businessmen were raking it in, too. A presidential inauguration is a great event for the country. It is a quadrennial gold mine for the local business community, especially the city's tourist industry - which is normally very slow in January.

Hotels here are full, black Cadillacs have been brought in from as far away as Philadelphia nad New York to handle the limousine liberals while real, honest-to-goodness Carter peanuts were being hawked yesterday along Pennsylvania Avenue NW.

Democrats have a reputation among businessman for being more free-spending than their Republican brethren, a proposition that could certainly not be disaproved this week.

Indeed, local hoteliers, restaurant owners, caterers and limousine service operators are so busy that they haven't time to tote up all their receipts.

Virtually every first-class hotel room in town, from the elegant Madison to the Capitol Hilton (until recently the Statler Hilton) was booked months ago. Even hotels like the Ambassador, at 14th and K Streets NW, and the Parkside, on I between 13th and 14th Streets, were full.

The first class hotels were requiring a minimum stay of four days - paid in advance. Places like the Ambassador, where the Peanut Train people from Plains and Americus, Ga. stayed, accepted overnight guests - but were booked up nonetheless.

George Coupe, an executive at the Gray Line Co., said his firm rented out its 50 limousines, farmed out business to another 50 chauffeurs with their own limousines, rented 70 smaller cars "and we still can't handle the business."

Coupe estimated that, in all, there are 400 limousines normally available in the Washington area. He said all the cars were booked weeks ago, most with four-day minimums, at prices ranging from about $175 a day to $1,500 for the week.

"Everything that moves, you can rent," Coupe said yesterday.

At the Robin Hood Restaurant, located at 1422 K St. NW, owner Stanley Janulewicz said his business is 30 per cent ahead this year so far over last. "It's been very good and it's going to get better."

Ray Byrne, a liquor salesman who was at the Robin Hood trying to sell liquor to Janulewicz, said his business was up, too. Especially this week. "Bourbon sales are down nationally but this week everyone needs bourbon. There are a lot of Southerners in town," he said.

Eastern Airlines also reported an increase in its business - especially between Washington and Atlanta. A spokesman for the airline said Eastern had chartered several planes to Georgians for the inauguration and that regular flights between here and Atlanta were heavily booked. "The increase is noticeable," the Eastern spokesman said. "Friday will be the heaviest day."

Northwest Airlines also said that seats on its flights between Washington and Minnesota, the home state of Vice President Walter Mondale, were in short supply for the next few days.

Not every business in town was doing as well as the hotels, restaurants, airlines and limousine rental companies. Pornographic bookstores and topless-bottomless bars along 14th Street NW are not doing well, according to their managers.

Larry Rentschler, manager of Benny's Rebel Room, which has both movies and go-go dancers, explained that "most of these tourists are families or church groups. They can't really come out to a bar like this."

Some vendors selling scarves, gloves, Carter-Mondale memorabilia and Plains peanuts at yesterday's events did not, in many cases, do as well as they expected, either.

Lee Jarvis, a vendor from Ocean City, Md., who was selling mirrors decorated with peanut bags for $15 apiece early yesterday, lowered the price to $10 late in the day "just so I can sell them off and get the hell out of the cold."

Another vendor, selling Carter-Mondale posters neat the parade-route, reduced his price from $3 to $1. "I've got to recoup my investment," he said. "This isn't a buying crowd."