I want to make a car model but I want to be able to make the model with the mirroring way but I also want to be able to select the different sides of the model individual. For example I want to make a hole in the left door without having the same hole in the right door.
It will be difficult in this way, you may make it simple in following ways;
First work for the model in all aspect in which both sides are same - using mirror
When you satisfied with your model apply the mirror.
Secondly, Now you are able to select any side as per your need and change any side individually