One free modeling app is anim8or (anim8or.com), which I've never used, but which some here seem to like a lot. Eovia.com also offeres an earlier version of their amapi modeler through various sites, such as bakhter.com. There are tutorials on these apps on the web...you could click on the tutorial link at the top of this page, then to offsite links, then click modelling to find a few of them. There's also an amapi forum here at R'osity, and I'm pretty sure folks there create tutorials. There may be other free modelers, but none leap to mind at 1:20 a.m...well, there was Blender, but i think it's gone the way of the dinosaur;-)