The rise in office real estate income has slowed.

Growth in net operating income from office buildings was almost flat in 1984, the Building Owners and Managers Assn. reported. The report reflects a downward trend over the past few years. The association said that operating income is not likely to grow for U.S. private-sector buildings in 1985 and may decline. Vacancy rates ran as high as 25% in some cities, the association said. In addition to the overbuilt situation facing building owners, the survey said costs for energy went up 8 cents per square foot from 1983 to 1984 and property taxes increased 11 cents per square foot.