The development of information and telecommunication technologies has given an opportunity to people to communicate among themselves without limitations in time and place.dependence from time and a place. At the initial stage of the development of social networks people united in groups, using e-mails, and followed changes on the Internet. Now the social networks are one of the business forms. Social networks and their services provide necessary appeal and a feedback to potential users. The information, collected in a social network, becomes enough valuable for using in commercial objectives. Modern social networks provide any activity (business, creative work, etc.) with the necessary information. The social network has the life cycle with some features. Cost of a social network differs on each of life cycle stages. Therefore the holder of a social network has to develop it constantly offering innovative services in the network. The social networks can be used in business differently: search for personnel and its selection, training, search for investors, advertising etc. Taking into account the practice of social networks and experience of the authors, it is possible to note the following incomes of the business based on the social networks: • Incomes from advertising; • Incomes from any paid services; • Incomes from sale of client base. For maintenance of incomes of the social networks their owners face such costs: • Costs of the maintenance of a social network (material costs, wages, taxes etc.); • Ammortisation of not-financial actives (licence); • Deterioration of technical maintenance. Usually business angels and risk capitalists finance the business of social networks at initial stage. They are interested to pay back their investment in 5-7 years. That is why there is a problem of cost estimation of a social network. There are various methods of cost estimation of social networks. In the given work the authors show such estimation based on the social network Flameable.lv.