YEs, it is possible to design one own home. However it is best that a prospective home buyer consult with a building professional in order to insure the house is of the highest quality, and is physically able to be built from both a material and safety point of view
Yes, in fact there are many programs to assist you in doing this. If you only want a basic visual idea, Google Sketchup would be perfect, and is free. If you want to get into the more advanced design, try Revit or autoCAD.
