How to hide a Model property for certain users?

Question

I am building an API that will serve users with different administration levels (roles)

I have the following model (redacted for brevity)

public class Job
{
    public Guid JobId { get; set; }
    public string Name{ get; set; }
    public string CommentsAdmins { get; set; }
}

When an admin user calls the API controller, I want the API to return the entire model above. But when a regular user calls the API, I want the model to return the same model, minus CommentsAdmins

public class Job
{
    public Guid JobId { get; set; }
    public string Name{ get; set; }
}

I'm not comfortable to use a nullable string? because I believe that's a dirty way to do it. Also I don't want the field to be visible in my mobile app code, which may be publicly visible if somebody tries to decompile the mobile app binaries.

Additionally, creating multiple models for multiple user levels doesn't feel intuitive as well.

What's the best way to go about this?