Can't set timer

I built a code watching Burgzerger Arcade but the problem is I just can't set the spawn time in 2 seconds. Can you check the code please.

 using UnityEngine;
 using System.Collections;
 using System.Collections.Generic;
 
 public class MobGenerator : MonoBehaviour 
 {
     public enum State
     {
         Idle,
         Initialize,
         Setup,
         SpawnMob
     }
 
     public GameObject[] mobPrefabs;
     public GameObject[] spawnPoints;
 
     public State state;
 
     private bool check = true;
 
     void Awake()
     {
         state = MobGenerator.State.Initialize;
     }
 
     IEnumerator Start () 
     {
         while (true)
         {
             switch(state)
             {
                 case State.Initialize:
                     Initialize();
                     break;
                 case State.Setup:
                     Setup();
                     break;
                 case State.SpawnMob:
                     SpawnMob();
                     break;
                 case State.Idle:
                     Idle();
                     break;
             }
 
             yield return 0;
         }
     }
 
     private void Initialize()
     {
         if (!CheckMobPrefabs())
             return;
 
         if (!CheckSpawnPoints())
             return;
 
         state = MobGenerator.State.Setup;
     }
 
     private void Setup()
     {
         state = MobGenerator.State.SpawnMob;
     }
 
     private void SpawnMob()
     {
         GameObject[] gos = AvailableSpawnPoints();
 
         for (int cnt = 0; cnt < gos.Length; cnt++)
         {
             GameObject go = Instantiate(mobPrefabs[Random.Range(0, mobPrefabs.Length)],
                                         gos[cnt].transform.position,
                                         Quaternion.identity
                                         ) as GameObject;
 
             go.transform.parent = gos[cnt].transform;
         }
         state = MobGenerator.State.Idle;
     }
 
     private void Idle()
     {
         Debug.Log("hi" + Time.time);
         if(check)
             StartCoroutine("Wait");
         Debug.Log("what" + Time.time);
     }
 
     private bool CheckMobPrefabs()
     {
         if (mobPrefabs.Length > 0)
             return true;
         else
             return false;
     }
 
     private bool CheckSpawnPoints()
     {
         if (spawnPoints.Length > 0)
             return true;
         else
             return false;
     }
 
     private GameObject[] AvailableSpawnPoints()
     { 
         List<GameObject> gos = new List<GameObject>();
 
         for (int cnt = 0; cnt < spawnPoints.Length; cnt++)
         {
             if (spawnPoints[cnt].transform.childCount == 0)
             {
                 Debug.Log("*** Spawn Points Available ***");
                 gos.Add(spawnPoints[cnt]);
             }
         }
         return gos.ToArray();
     }
 
     IEnumerator Wait()
     {
         Debug.Log("hop");
         check = false;
         yield return new WaitForSeconds(2);
         check = true;
         state = MobGenerator.State.SpawnMob;        
         Debug.Log("ono");
     }
 
 }