Builder Pattern involving complex objects

For fundamental types the builder pattern seems to be pretty straight forward. I wanted to understand how it works when you want to build an object having complex member types.

Here I have a Person class and a static inner class to build Person. I have an Address Class that I have defined in the PersonBuilder static nested class. Ideally the Address Class should have been defined in the Person class itself. The code works but I am not sure If I am doing things correctly here. Can anyone please advise if there is a better way to construct these kind of objects.

class Person{

private String firstName;
private String lastName;
private Integer age;
private Person.PersonBuilder.Address address;

private Person(PersonBuilder builder){
    this.firstName =  builder.firstName;
    this.lastName = builder.lastName;
    this.age = builder.age; 
    this.address = builder.address;
}

@Override
 public String toString(){
    return "Person: " + 
           this.firstName + "|" + 
           this.lastName + "|" + 
           this.age.toString() + "|" + 
           this.address.aptNum + "|" +
           this.address.street + "|" +
           this.address.city + "|" +
           this.address.state + "|" +
           this.address.zipCode;
}

public static class PersonBuilder{

    private String firstName;
    private String lastName;
    private Integer age;
    private Address address;

    private class Address{

        private String aptNum;
        private String street;
        private String city;
        private String state;
        private Long zipCode;

        public Address(String aptNum, String street, String city, String state, Long zipCode) {
            this.aptNum = aptNum;
            this.street = street;
            this.city = city;
            this.state = state;
            this.zipCode = zipCode;
        }
    }       

    public PersonBuilder(String firstName, String lastName){
        this.firstName = firstName;
        this.lastName = lastName;
        this.address = this.new Address("", "", "", "", 0L);
    }

    public PersonBuilder age(Integer age){
        this.age = age;
        return this;            
    }

    public PersonBuilder buildAddress(String aptNum, String street, String city, String state, Long zipCode){
        this.address = new Address(aptNum, street, city, state, zipCode);
        return this;
    }

    public Person build(){
        return new Person(this);
    }
}

}

class Demo {
    public static void main(String[] args){
        Person p1 = new Person.PersonBuilder("XYZ", "XYZ")
                              .age(24)
                              .buildAddress("AB", "XYZ Lane", "ABCtown", 
                              "XY", 1234L)
                              .build();

                 System.out.println(p1.toString());
     }
}