If you don't have the time or the patience, this is the way to go. However, ARF's tend to be a little more expensive than kits. If you are still somewhat of a novice builder, but would like to take the time to construct a plane from plans, the results can also be very rewarding. There is significantly more effort in the construction process because all the parts must be hand cut to fit the plans. In most kits, the parts are usually die cut, or ink stamped on the materials on where to cut.
Most kits come with detailed construction and assembly instructions.
This is when you measure, or research the specification of a full size plane and create your own set of construction plans and details. It is very time consuming, but if you are a purist, it is worth the effort. The biggest problem that a scratch builders face is making sure that the model is not to heavy, or is over constructed. Models or real planes don't fly well or at all, if they are too heavy. If a plane is very light, ask yourself if is it strong enough.