Despite many advantages that could be gained through belonging to enterprise networks, only a few networks continue running businesses after the governments stop their funding. One of the reasons is the lack of a model that evaluates the benefits from the firm's point of view. The objective of this work is to develop a model that estimates the benefits in horizontal collaborative networks, for a considered business opportunity, and determines the optimal network configuration in terms of the selected enterprises. We propose a method for evaluating the profits for a collaborative network based on a combination of product realisation graph and core competences identification. Through the case study of a Swiss horizontal collaborative network, the proposed approach proves its efficiency in selecting the optimal network of partners and evaluating their corresponding turnover and profits.