UPPER MARLBORO, Md. (AP) _ Wanted: 400 teachers. Fringe benefits: cheap car loans, restaurant discounts, a summer job and one month's free rent.

Prince George's County, Md., schools, which have the lowest starting teacher's salary in the Washington, D.C., area, are trying to get an edge on the competition for teachers in a seller's market by offering some unusual extras to those who are hired before August 1.

The idea came from businesspeople who have been working with the 103,000- pupil school system the last two years with the belief that strong schools are good for business.

''The school system is the heart of the community,'' said Winfield Kelly, president of the Advisory Council for Business and Industry, which organized the program. ''If it is strong and healthy than everyone else in the community will benefit.''

The business leaders, who raised more than $200,000 for a recent television advertising campaign promoting the schools, also are instructing the system's personnel staff in corporate recruiting techniques to get the best teachers.

The council will host a ''hospitality suite'' in April at the Boston Consortium, where 130 school systems will vie for prospective teachers. It will do the same at a similar program at the University of Maryland in May.

Kelly says that if the incentives the schools are offering applicants work ''some of the brightest and most gifted teachers in the Northeast will be coming here.''

''Just like everyone, we are competing for a small number of applicants,'' said Jacquelyn Lendsey, spokeswoman for the Prince George's County school system, which, at full force, has 5,000 teachers.

The system has the lowest starting salary in the metropolitan area - $15,738 - though an increase to $19,000 next year will make the schools competitive, Mrs. Lendsey said.

''But we are also going to have an extra edge by offering these discounts,'' she said.

The new teachers will receive:

-A month's free rent at their choice of 12 apartment complexes, which also will waive security deposits.

-Discounts on all consumer and auto loans and bank credit cards without an annual fee at two local banks.

-A 20 percent discount at three restaurant chains in the area.

-Summer employment in professional positions with local businesses.

The National Center for Education Statistics predicts that the current national teacher drought will accelerate and, by 1992, the schools could be 232,000 teachers short of the number needed.

Howard Carroll, spokesman for the National Education Association, said a big push is on nationally to involve business and industry in the schools.

He said he had not heard of another program exactly like the one in Prince George's County.

''Any time business and industry wants to help schools and attract young people to teaching, that's fine,'' Carroll said. ''As a young person looking for a job, this would be appealing.

''We're not going to knock anything that is going to help, but this is not a panacea for all the problems,'' he said, listing other teacher grievances including class size, materials, administrative support and school conditions.

Mrs. Lendsey said teachers in the county are voting on a new contract to increase salaries and provide other benefits, though the discounts being offered to applicants are not included.

''We believe the teachers with us understand the need to attract good teachers to the system. This is a beginning. It does not mean that at some point the business community will not do something for teachers already in the system,'' she said.