All 3d models you can find here for the TW sims are created with a version of 3ds Max.
For your first steps on 3d modeling i would recommend the program "GMax". It´s from the same company like 3ds Max, with minor options, but totally free. When i remember correct, you must only register to download the full program.
Indeed it looks and works almost the same like 3ds Max, only problem is, the models cannot been brought into the game, cause the TW LOD exporter isn´t working with GMax and you cannot save the model in a format, 3ds can open. Only way is to export the model into a "*.3ds" file, wich can be imported by 3ds Max. But there are losses of animations and texture coordinates, along some other little things wich can cause you to drive crazy!