The Arlington County Board told its new county manager yesterday to come up with a balanced budget for the next fiscal year that will allow the county real estate tax rate to stay the same.

County Manager Larry J. Brown said he expects to to propose a fiscal 1984 budget in February that will include "enough options" to keep the tax rate at 98 cents per $100 of assessed valuation. Brown, who was hired in August, said he plans a comprehensive review of all county programs and that program and job reductions might result.

"It's very doubtful you're going to be considering adding programs at increased costs and very likely you're going to be facing which programs to sustain at increased costs," said Brown, a former Minnesota county executive who oversaw local funding cuts in that state.

Brown last month recommended a $174.2 million county budget for next year, a 5 percent increase over this fiscal year's budget. The proposed budget includes a $50.7 million contribution to county schools and $16.1 million for the Metro system. The board approved both recommended guidelines yesterday.

Because of the slumping real estate sales and smaller-than-anticipated real estate tax collections, inflation and federal budget cuts, the county is expected to fall $6.7 million short of its projected needs, Brown said.

The recommended school budget guideline is an increase of about 5 percent over this year's county share of school costs and would allow a modest salary increase, officials said. The schools need at least $49.4 million to run at their present level without pay raises, officials have said.

The recommended Metro budget guideline represents a 12 percent increase over this year's county subsidy. Metro officials have indicated they may seek an increase of 26 to 36 percent.

"Pressure must be placed on the Metro board and management to understand that Metro's anticipated subsidy increases are not tolerable for Arlington," Brown wrote in a memo to the board.

In other action, the board's Republican-backed majority voted to oppose the creation of an Arlington redevelopment and housing authority, an issue that will be on the Nov. 2 ballot. GOP-endorsed independents, Stephen H. Detwiler, Board Chairman Walter L. Frankland and Dorothy T. Grotos had previously announced their opposition.

The board's two other members, Democrat John G. Milliken and Democrat-backed independent Ellen M. Bozman had endorsed an authority previously and voted for it yesterday.