This paper evaluates the impact of agricultural price and intensification policies for common property resources and welfare of rural communities in developing countries. In doing so we develop a new model for the farm-household that has analytical advantages over the traditional one and that has significant potential for empirical application. The major findings are: Technical assistance that increase productivity of land-intensive agricultural outputs (cereals, livestock, etc.) cause degradation of the communal resources and may cause immiserization. Policies that increase the prices of these goods cause identical effects. By contrast, similar policies applied to labor-intensive outputs (vegetables, tubers, etc.) contribute to improve the common resources and to increase the welfare of the rural communities.