Physical models of patient anatomy have been used increasingly as 3D printing technologies have become mainstream. Such models can be used for both the validation of new minimally invasive surgical techniques, as well as surgical rehearsal and training. However, current workflows for creating flexible models with complex anatomy rely on the use of expensive 3D printing techniques. We present a mold design with which we create patient-specific physical models using low-cost techniques and materials. This generic mold makes it possible to create physical models with multiple components and complex internal structures including tumours, vasculature and other anatomic components with accuracy. To demonstrate this, we have created kidney models derived from the CT of excised porcine kidneys, including vasculature and an artificial tumor. We created the models in two parts, first using a rigid positive model to create a negative mold, and then creating a silicone model with the 3D printed vasculature inside, and removing it to leave wall-less vessels. The vasculature models include at least six separate bifurcations with minimum lumen diameters of approximately 1mm. The mean Euclidean offset distance between the model and original vessels was 0.42 mm, with a standard deviation of 0.50 mm. Both generic and patient specific models can be built with this workflow.