Best way to run a switchable 1st to 3rd person camera system?

Currently I have this for switching between 3rd person and 1st person.

pragma strict

var ThePlayer : GameObject; var FirstPersonCam : Camera; var ThirdPersonCam : Camera; var Check;

function Start () {

 ThirdPersonCam.depth = Camera.main.depth + 1;
 FirstPersonCam.depth = Camera.main.depth - 1;

 Check = true;        

}

function Update () {

 if(Input.GetKeyDown(KeyCode.V)){
     if(Check){
         FirstPersonCam.depth = Camera.main.depth + 1;
         ThirdPersonCam.depth = Camera.main.depth - 1;

     }

     else{
         FirstPersonCam.depth = Camera.main.depth - 1;
         ThirdPersonCam.depth = Camera.main.depth + 1;

     }

     Check = !Check;

 }

}

 //ThirdPersonCam.cullingmask = -1;
 //FirstPersonCam.cullingmask = 0;

        //ThirdPersonCam.cullingmask = 0;
 //FirstPersonCam.cullingmask = -1;


    //ThirdPersonCam.nearClipPlane = .3f;
 //ThirdPersonCam.farClipPlane = 1000;

 //FirstPersonCam.nearClipPlane = 1000;
 //FirstPersonCam.farClipPlane = .3f;

I chose to keep both of them enabled for the fact that they aren't children to each other and when one is disabled and then re-enabled it would be looking in the last direction it was when it was last enabled, instead of the same direction that the previous camera was looking in. I'm concerned that having two cameras rendering at the same time is going to drop fps. I commented in some ideas that I tried, but they ended up not working. (Plus I didn't know what number "nothing" was for culling mask so if culling mask could work I would only need to know what the number for "nothing" is, since -1 is everything. Any Ideas? Thanks!