When to create a navigation property in model - asp.net-mvc

Question

As a new programmer I am trying to understand when I should create navigation properties for my Models. What are the trade offs?
On the extremes, the model can just contain ever field need, or the base model can have navigation properties for every field?
Or should navigation property only be used for complex related entities (an entity with more than one property)?
Another consideration I am considering is what works best for MVC drop down or jquery autocomplete. How will designing the model impact application and sql performance?
public class Vendor
{
public int ID { get; set; }
public string Name { get; set; }
public string Number { get; set; }
public string Address { get; set; }
public string City { get; set; }
public string State { get; set; }
public string PostalCode { get; set; }
public string Country { get; set; }
}
or I could do this and assume the related tables also exists in the namespace and in turn the database.
public class Vendor
{
public int ID { get; set; }
public virtual Name Name { get; set; }
public virtual Number Number { get; set; }
public virtual Street Street { get; set; }
public virtual City City { get; set; }
public virtual State State { get; set; }
public virtual PostalCode PostalCode { get; set; }
public virtual Country Country { get; set; }
}
I can see that some of the related entities will be static in nature like States but Number and Street will grow over time.

Answer 1

If your property can be represented by a simple database column, then you use the first approach, if you property itself has its own properties, then you will need a navigational property. If your case, if the City also has properties such as Id, Name, etc, then you will use the navigation property, however, if you only want to store city as the name, your first approach will work.