Daily.
If you want to earn money from it I suggest you decide on an industry. 3DS Max is big in gaming and visualization. Rhino and SketchUp is great for the construction industry. I've worked a bit in Blender and if you know your way around it the step to the others won't be so big.
You should try Unreal Engine as it's free. I've done some visuals in it. Or CryEngine.