Zealot

i'm totally ignorant of any kind of 3d model kits for free. it sounds like a great hobby, I have fooled around in google sketch and metasequoia, but was unable to save anything I drew. I loved making plastic models and paper models and would like to pass some time piecing together 3d rotatable virtual assembly free kits. can some expert on this start me out and maybe pass on a few pointers? some others here might be interested too.
thanks!
jim