A quick question C#

Ok I understand your problem now. You should read up on variable scope http://www.codecandle.com/articles/csharp/variables/variable-scope.html

You set up the questing bool as a public variable inside your class. While you set up float timer as a variable inside a method(function) of your class.

Nothing outside a class can see whats inside a classes functions, they can only see whats set to public in the class itself. So, to access the timer, change your code to this

 using UnityEngine;
 using System.Collections;
  
 public class Quests : MonoBehaviour 
 {
     public static bool Questing;
     public float timer;
 
     public static void OnGui () 
     {
         // Is Questing Allowed?
         if(Questing == false)
         {
             GUI.Box(new Rect(10,10,10,10),"No Quests!!!");
         }
 
         if (Questing == true)
         {     
             Money.enabled = true;
         }
     }
 
     void rewards () 
     {
  
     }
 }

However, this is considered bad programming practice. Ideally, you want to make all the variables private and create get/set public methods for each one.

 using UnityEngine;
 using System.Collections;
 
 public class Quests : MonoBehaviour 
 {
     private bool Questing;
     private float timer;
 
     void OnGui () 
     {
         //Shortened code
     }
 
     void rewards () 
     {
 
     }
 
     public bool getQuesting()
     {
         return Questing;
     }
     public float getTimer()
     {
         return timer;
     }
     public void setQuesting(bool newValue)
     {
         Questing = newValue;
     }
     public void setTimer(float newValue)
     {
         timer = newValue;
     }
 }

Now the only way to read/change the private classes variables are by using special public methods. This ensures that you never make any mistakes, and is just considered proper coding.