This work negotiates some basic principles and problems in Greek rural economy, as demand and supply elasticity, the economic development in this sector, as capital accumulation, financing investment and investment function. Other subjects which are examined in this book are the sponge production using the model of adaptive expectations, Cobb-Douglas model to examine the output scales in rural sector, a model to determine demand elasticities for fertilizers, co-integration and ARIMA methodology, as well two macroeconomic models in closed economy using simultaneous equations. The methodology approach which is followed is simple in such a way to provide the reader the basic knowledge and understanding of different econometrical techniques and errors, like heteroskedasticity, multicollinearity and autocorrelation. The purpose of this work is to provide tools which can be used for further research, practicing and improvement. So for this reason this book is addressed to undergraduate and postgraduate students in economic studies as well to professionals who apply economic policy.