Software Product Lines is still a new field within software reuse that aims at large-scale, systematic reuse. Hugh benefits regarding the reduction of time-to-markets, reduction of effort, and quality improvement have been reported as a result of adopting a product line approach. Since a product line program involves major investments, considerable risks are associated with it. Thus, it is important to evaluate at the start of a product line project, i.e., before the major investments are performed, its potential benefits and risks.In this paper we describe an approach that allows to identify the benefits and risks in a systematic manner, thus enabling the early development of risk-avoiding measures. As opposed to other techniques our approach supports the identification of subdomains that are particular appropriate for systematic reuse and by means of the detailed evaluation enables trade-off decisions on where to invest for reuse.