diff --git a/lesson_17/bank/bank_app/src/main/java/com/codedifferently/lesson17/bank/BusinessCheckingAccount.java b/lesson_17/bank/bank_app/src/main/java/com/codedifferently/lesson17/bank/BusinessCheckingAccount.java
new file mode 100644
index 000000000..d43990435
--- /dev/null
+++ b/lesson_17/bank/bank_app/src/main/java/com/codedifferently/lesson17/bank/BusinessCheckingAccount.java
@@ -0,0 +1,29 @@
+package com.codedifferently.lesson17.bank;
+
+import java.util.Set;
+
+public class BusinessCheckingAccount extends CheckingAccount {
+  public BusinessCheckingAccount(String accountNumber, Set<Customer> owners, double balance) {
+    super(accountNumber, owners, balance);
+    if (!hasBusinessOwner(owners)) {
+      throw new IllegalArgumentException("requires at least one business owner.");
+    }
+  }
+
+  private boolean hasBusinessOwner(Set<Customer> owners) {
+    return owners.stream().anyMatch(Customer::isBusiness);
+  }
+
+  @Override
+  public String toString() {
+    return "BusinessCheckingAccount{"
+        + "accountNumber='"
+        + accountNumber
+        + '\''
+        + ", balance="
+        + balance
+        + ", isActive="
+        + isActive
+        + '}';
+  }
+}
diff --git a/lesson_17/bank/bank_app/src/main/java/com/codedifferently/lesson17/bank/BusinessOwner.java b/lesson_17/bank/bank_app/src/main/java/com/codedifferently/lesson17/bank/BusinessOwner.java
new file mode 100644
index 000000000..8e7eae7b5
--- /dev/null
+++ b/lesson_17/bank/bank_app/src/main/java/com/codedifferently/lesson17/bank/BusinessOwner.java
@@ -0,0 +1,22 @@
+package com.codedifferently.lesson17.bank;
+
+import java.util.UUID;
+
+public class BusinessOwner extends Customer {
+
+  private final String businessName;
+
+  public BusinessOwner(UUID id, String name, String businessName) {
+    super(id, name);
+    this.businessName = businessName;
+  }
+
+  public String businessName() {
+    return businessName;
+  }
+
+  @Override
+  public boolean isBusiness() {
+    return true;
+  }
+}
diff --git a/lesson_17/bank/bank_app/src/main/java/com/codedifferently/lesson17/bank/Check.java b/lesson_17/bank/bank_app/src/main/java/com/codedifferently/lesson17/bank/Check.java
index 061fa4a5c..ea449167d 100644
--- a/lesson_17/bank/bank_app/src/main/java/com/codedifferently/lesson17/bank/Check.java
+++ b/lesson_17/bank/bank_app/src/main/java/com/codedifferently/lesson17/bank/Check.java
@@ -21,6 +21,9 @@ public Check(String checkNumber, double amount, CheckingAccount account) {
     if (amount < 0) {
       throw new IllegalArgumentException("Check amount must be positive");
     }
+    if (account instanceof SavingsAccount) {
+      throw new UnsupportedOperationException("Cannot issue checks from a savings account.");
+    }
     this.checkNumber = checkNumber;
     this.amount = amount;
     this.account = account;
diff --git a/lesson_17/bank/bank_app/src/main/java/com/codedifferently/lesson17/bank/CheckingAccount.java b/lesson_17/bank/bank_app/src/main/java/com/codedifferently/lesson17/bank/CheckingAccount.java
index 5d8aeb74d..42632cc20 100644
--- a/lesson_17/bank/bank_app/src/main/java/com/codedifferently/lesson17/bank/CheckingAccount.java
+++ b/lesson_17/bank/bank_app/src/main/java/com/codedifferently/lesson17/bank/CheckingAccount.java
@@ -7,9 +7,9 @@
 public class CheckingAccount {
 
   private final Set<Customer> owners;
-  private final String accountNumber;
-  private double balance;
-  private boolean isActive;
+  public final String accountNumber;
+  protected double balance;
+  protected boolean isActive;
 
   /**
    * Creates a new checking account.
diff --git a/lesson_17/bank/bank_app/src/main/java/com/codedifferently/lesson17/bank/Customer.java b/lesson_17/bank/bank_app/src/main/java/com/codedifferently/lesson17/bank/Customer.java
index af0847134..5fc5cbe17 100644
--- a/lesson_17/bank/bank_app/src/main/java/com/codedifferently/lesson17/bank/Customer.java
+++ b/lesson_17/bank/bank_app/src/main/java/com/codedifferently/lesson17/bank/Customer.java
@@ -58,6 +58,11 @@ public Set<CheckingAccount> getAccounts() {
     return accounts;
   }
 
+  // defaults accounts to non-business Owners.
+  public boolean isBusiness() {
+    return false;
+  }
+
   @Override
   public int hashCode() {
     return id.hashCode();
diff --git a/lesson_17/bank/bank_app/src/main/java/com/codedifferently/lesson17/bank/SavingsAccount.java b/lesson_17/bank/bank_app/src/main/java/com/codedifferently/lesson17/bank/SavingsAccount.java
new file mode 100644
index 000000000..a289f2ce9
--- /dev/null
+++ b/lesson_17/bank/bank_app/src/main/java/com/codedifferently/lesson17/bank/SavingsAccount.java
@@ -0,0 +1,24 @@
+package com.codedifferently.lesson17.bank;
+
+import java.util.Set;
+
+// represents a savings account
+public class SavingsAccount extends CheckingAccount {
+
+  public SavingsAccount(String accountNumber, Set<Customer> owners, double balance) {
+    super(accountNumber, owners, balance);
+  }
+
+  @Override
+  public String toString() {
+    return "SavingsAccount{"
+        + "accountNumber='"
+        + accountNumber
+        + '\''
+        + ", balance="
+        + balance
+        + ", isActive="
+        + isActive
+        + '}';
+  }
+}
diff --git a/lesson_17/bank/bank_app/src/test/java/com/codedifferently/lesson17/bank/BusinessCheckingAccountTest.java b/lesson_17/bank/bank_app/src/test/java/com/codedifferently/lesson17/bank/BusinessCheckingAccountTest.java
new file mode 100644
index 000000000..7450c30d2
--- /dev/null
+++ b/lesson_17/bank/bank_app/src/test/java/com/codedifferently/lesson17/bank/BusinessCheckingAccountTest.java
@@ -0,0 +1,36 @@
+package com.codedifferently.lesson17.bank;
+
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.HashSet;
+import java.util.Set;
+import java.util.UUID;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+public class BusinessCheckingAccountTest {
+  private Customer regularCustomer;
+  private BusinessOwner BusinessCustomer;
+  private Set<Customer> owners;
+
+  @BeforeEach
+  void setUp() {
+    regularCustomer = new Customer(UUID.randomUUID(), "james");
+    BusinessCustomer = new BusinessOwner(UUID.randomUUID(), "john", "long johns");
+    owners = new HashSet<>();
+  }
+
+  @Test
+  void hasBusinessOwnerTest() {
+    owners.add(regularCustomer);
+
+    IllegalArgumentException thrown =
+        assertThrows(
+            IllegalArgumentException.class,
+            () -> new BusinessCheckingAccount("12354", owners, 100.00),
+            "Expect Constructor to throw but did not");
+
+    assertTrue(thrown.getMessage().contains("requires at least one business owner"));
+  }
+}
diff --git a/lesson_17/bank/bank_app/src/test/java/com/codedifferently/lesson17/bank/SavingsAccountTest.java b/lesson_17/bank/bank_app/src/test/java/com/codedifferently/lesson17/bank/SavingsAccountTest.java
new file mode 100644
index 000000000..d07b93a04
--- /dev/null
+++ b/lesson_17/bank/bank_app/src/test/java/com/codedifferently/lesson17/bank/SavingsAccountTest.java
@@ -0,0 +1,31 @@
+package com.codedifferently.lesson17.bank;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.util.HashSet;
+import java.util.Set;
+import java.util.UUID;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+public class SavingsAccountTest {
+  private SavingsAccount classUnderTest;
+  private Set<Customer> owners;
+
+  @BeforeEach
+  void setUp() {
+    owners = new HashSet<>();
+    owners.add(new Customer(UUID.randomUUID(), "John Doe"));
+    owners.add(new Customer(UUID.randomUUID(), "Jane Smith"));
+    classUnderTest = new SavingsAccount("123456789", owners, 100.0);
+  }
+
+  @Test
+  void toStringTest() {
+    // arrange
+    String expected = "SavingsAccount{accountNumber='123456789', balance=100.0, isActive=true}";
+
+    // assert
+    assertEquals(expected, classUnderTest.toString());
+  }
+}