Real Estate Activities On A Fee Or Contract Basis ISIC Code 6820. This class includes the provision of real estate activities on a fee or contract basis including real estate-related services. This class includes activities of real estate agents and brokers, intermediation in buying, selling, and renting of real estate on a fee or contract basis, management of real estate on a fee or contract basis, appraisal services for real estate, activities of real estate escrow agents, special education for handicapped students at this level, provision of literacy programs for adults.