Database model for users with multiple capabilities

Question

In another question, I explain my goal to create 2 different types of users with different capabilities in my ASP.Net MVC 5 website. I wonder how I would be able to modify my current database models to hold the related information based on their type. My current models are as follows:

public class User : IUser
{
    public User()
        : this(String.Empty)
    {
    }

    public User(string userName)
    {
        UserName = userName;
        Id = Guid.NewGuid().ToString();
    }

    [Key]
    public string Id { get; set; }

    [Required]
    public string UserName { get; set; }

    [Required]
    public string FirstName { get; set; }

    [Required]
    public string LastName { get; set; }

    public string Phone { get; set; }
    public string MobilePhone { get; set; }

    [Required]
    [DataType(DataType.EmailAddress)]
    public string Email { get; set; }

    public virtual IList<UserAddress> Addresses { get; set; }
}

public class Restaurant
{
    [Key]
    public int ID { get; set; }

    [Required]
    public string Name { get; set; }

    public virtual IList<RestaurantAddress> Addresses { get; set; }

    public virtual IList<RestaurantFood> Menu { get; set; }

    public virtual IList<Review> Reviews { get; set; }

    [DataType(DataType.Url)]
    public string Website { get; set; }

    [DataType(DataType.PhoneNumber)]
    public string Phone { get; set; }

    [DataType(DataType.PhoneNumber)]
    public string Fax { get; set; }

    [DataType(DataType.EmailAddress)]
    public string Email { get; set; }

    public int Seats { get; set; }

    public double AverageRating { get; set; }
    public double AveragePrice { get; set; }
}

One solution that comes to my mind is to move the additional info of the User class to another class and hold the foreign key for the related model in the basic user info class. Something like:

public class User : IUser
{
    public User()
        : this(String.Empty)
    {
    }

    public User(string userName)
    {
        UserName = userName;
        Id = Guid.NewGuid().ToString();
    }

    [Key]
    public string Id { get; set; }

    [Required]
    public string UserName { get; set; }

    public virtual ExtendedUser NormalUserInfo { get; set; }
    public virtual Restaurant RestaurantInfo { get; set; }
}

public class ExtendedUser
{
    [Required]
    public string FirstName { get; set; }

    [Required]
    public string LastName { get; set; }

    public string Phone { get; set; }
    public string MobilePhone { get; set; }

    [Required]
    [DataType(DataType.EmailAddress)]
    public string Email { get; set; }

    public virtual IList<UserAddress> Addresses { get; set; }
}

public class Restaurant
{
    [Key]
    public int ID { get; set; }

    [Required]
    public string Name { get; set; }

    public virtual IList<RestaurantAddress> Addresses { get; set; }

    public virtual IList<RestaurantFood> Menu { get; set; }

    public virtual IList<Review> Reviews { get; set; }

    [DataType(DataType.Url)]
    public string Website { get; set; }

    [DataType(DataType.PhoneNumber)]
    public string Phone { get; set; }

    [DataType(DataType.PhoneNumber)]
    public string Fax { get; set; }

    [DataType(DataType.EmailAddress)]
    public string Email { get; set; }

    public int Seats { get; set; }

    public double AverageRating { get; set; }
    public double AveragePrice { get; set; }
}

and in controller:

    User user = BuildUser();
    ExtendedUser normal = BuildNormalUser();
    Restaurant rest = BuildRestaurant();
    if (model.Type == UserType.NormalUser)
        user.NormalUserInfo = normal;
    else
        user.RestaurantInfo = normal;

However, I'm not sure that this is the right thing to do.