Financially, project portfolios can be completely self-reliant when their required liquidity is merely obtained through reinvesting the profit of the finished projects and the initial capital of the owners. However, the firm can only perform some profitable projects despite maximizing wealth owing to a shortage of funds. In such cases, projects’ implementation can be phased as a practical solution to satisfy financial deficiencies. Therefore, decision-makers are involved in finding the optimum selection and scheduling of the self-financing phase-able project portfolios. Some projects especially construction projects encompass a multi-stage process of repetitive activities, which pave the way for taking advantage of the economy of scale when organizing for development. This research proposes a mathematical model for the problem of building construction project portfolio with simultaneous consideration of the reinvestment strategy, phasing strategy, and economy of scale at the enterprise level. In this case, an integer programming model to maximize the investment's net present value is presented. The proposed model provides a decition support system for property developers to select and schedule self-financing phase-able building construction project portfolios, in this context, the model's applicability is illustrated in a case example.