diff --git a/src/main/java/millions/model/Exchange.java b/src/main/java/millions/model/Exchange.java
index 46ab5ef..57d91fd 100644
--- a/src/main/java/millions/model/Exchange.java
+++ b/src/main/java/millions/model/Exchange.java
@@ -2,6 +2,7 @@
 
 import java.math.BigDecimal;
 import java.math.RoundingMode;
+import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Comparator;
 import java.util.HashMap;
@@ -20,6 +21,7 @@ public class Exchange {
   private Random random = new Random();
   private final TransactionFactory purchaseFactory = new PurchaseFactory();
   private final TransactionFactory saleFactory = new SaleFactory();
+  private final List<ExchangeListener> listeners = new ArrayList<>();
 
   public Exchange(String name, List<Stock> stockList) {
     this.name = name;
@@ -47,6 +49,7 @@ public Transaction buy(String symbol, Player player, BigDecimal quantity) {
 
     Transaction purchase = purchaseFactory.createTransaction(shareToBuy, weekNumber);
     purchase.commit(player);
+    notifyTransactionCompleted(purchase);
 
     return purchase;
   }
@@ -59,6 +62,7 @@ public Transaction sell(Share share, Player player) {
     Transaction sale = saleFactory.createTransaction(share, weekNumber);
 
     sale.commit(player);
+    notifyTransactionCompleted(sale);
     return sale;
   }
 
@@ -107,5 +111,26 @@ public void advance() {
               .setScale(2, RoundingMode.HALF_UP));
       // RoundingMode from AI suggestion
     }
+    notifyWeekAdvanced();
+  }
+
+  public void addListener(ExchangeListener listener) {
+    listeners.add(listener);
+  }
+
+  public void removeListener(ExchangeListener listener) {
+    listeners.remove(listener);
+  }
+
+  private void notifyWeekAdvanced() {
+    for (ExchangeListener listener : listeners) {
+      listener.onWeekAdvanced(weekNumber);
+    }
+  }
+
+  private void notifyTransactionCompleted(Transaction transaction) {
+    for (ExchangeListener listener : listeners) {
+      listener.onTransactionCompleted(transaction);
+    }
   }
 }
diff --git a/src/main/java/millions/model/Player.java b/src/main/java/millions/model/Player.java
index 4324bce..09f43d4 100644
--- a/src/main/java/millions/model/Player.java
+++ b/src/main/java/millions/model/Player.java
@@ -2,6 +2,8 @@
 
 import java.math.BigDecimal;
 import java.math.RoundingMode;
+import java.util.ArrayList;
+import java.util.List;
 
 public class Player {
   private String name;
@@ -11,6 +13,7 @@ public class Player {
   private TransactionArchive transactionArchive;
   // temporary attribute until a better solution is found
   public int weeksTraded;
+  private final List<PlayerListener> listeners = new ArrayList<>();
 
   public Player(String name, BigDecimal startingMoney) {
     this.name = name;
@@ -33,6 +36,7 @@ public void addMoney(BigDecimal amount) {
       throw new IllegalArgumentException("Amount cannot be null or negative");
     }
     this.money = this.money.add(amount);
+    notifyMoneyChanged();
   }
 
   public void withdrawMoney(BigDecimal amount) {
@@ -40,6 +44,7 @@ public void withdrawMoney(BigDecimal amount) {
       throw new IllegalArgumentException("Amount cannot be null or negative");
     }
     this.money = this.money.subtract(amount);
+    notifyMoneyChanged();
   }
 
   public String getStatus() {
@@ -70,6 +75,18 @@ public Portfolio getPortfolio() {
     return this.portfolio;
   }
 
+  public void addShareToPortfolio(Share share) {
+    this.portfolio.addShare(share);
+    notifyPortfolioChanged();
+    notifyStatusChanged();
+  }
+
+  public void removeShareFromPortfolio(Share share) {
+    this.portfolio.removeShare(share);
+    notifyPortfolioChanged();
+    notifyStatusChanged();
+  }
+
   public BigDecimal getNetWorth() {
     return this.money.add(this.portfolio.getNetWorth());
   }
@@ -77,4 +94,30 @@ public BigDecimal getNetWorth() {
   public TransactionArchive getTransactionArchive() {
     return this.transactionArchive;
   }
+
+  public void addListener(PlayerListener listener) {
+    listeners.add(listener);
+  }
+
+  public void removeListener(PlayerListener listener) {
+    listeners.remove(listener);
+  }
+
+  private void notifyMoneyChanged() {
+    for (PlayerListener listener : listeners) {
+      listener.onMoneyChanged(money);
+    }
+  }
+
+  private void notifyPortfolioChanged() {
+    for (PlayerListener listener : listeners) {
+      listener.onPortfolioChanged();
+    }
+  }
+
+  private void notifyStatusChanged() {
+    for (PlayerListener listener : listeners) {
+      listener.onStatusChanged(getStatus());
+    }
+  }
 }
diff --git a/src/main/java/millions/model/Purchase.java b/src/main/java/millions/model/Purchase.java
index 70bf608..59da2c0 100644
--- a/src/main/java/millions/model/Purchase.java
+++ b/src/main/java/millions/model/Purchase.java
@@ -18,7 +18,8 @@ public void commit(Player player) {
       throw new IllegalStateException("Not enought money");
     }
     player.withdrawMoney(getCalculator().calculateTotal());
-    player.getPortfolio().addShare(getShare());
+    // Don't reach directly to the portefolio object
+    player.addShareToPortfolio(getShare());
     player.getTransactionArchive().add(this);
     setCommitted(true);
   }
diff --git a/src/main/java/millions/model/Sale.java b/src/main/java/millions/model/Sale.java
index 79ef8b0..dbd3637 100644
--- a/src/main/java/millions/model/Sale.java
+++ b/src/main/java/millions/model/Sale.java
@@ -18,7 +18,7 @@ public void commit(Player player) {
       throw new IllegalStateException("Does not own the share");
     }
     player.addMoney(getCalculator().calculateTotal());
-    player.getPortfolio().removeShare(getShare());
+    player.removeShareFromPortfolio(getShare());
     player.getTransactionArchive().add(this);
     setCommitted(true);
   }