Google SketchUp
Blender
SketchUp has great tutorials and is easy to use. Good presentation faculties and can draw from photo. Not easy to make 3D prints with SketchUp. Must use various third party software to run through all the checks.
Blender is more advanced, harder to learn… but not that hard. Excellent tool for 3D printing as all the components are built right in. It renders better for higher quality animation than SketchUp.
Both systems are free and have vast tutorials and support. SketchUp has a Pro version with very limited extras provided.