As used in the School Revenue Bond Act:
A. "income project" means purchasing, erecting, improving, repairing or furnishing a building, improvement or facility, including the land upon which it is situated, which will produce an income to the school district;
B. "net income from the income project" means all income derived from an income project, including the income pledged pursuant to the School Revenue Bond Act, less the operating costs of the income project; and
C. "operating costs" means expenses of operating, maintaining and keeping in repair an income project, including the cost of heating, electricity, insurance, service employees and equipment replacement.