Correct usage of MVVM and object for method
Minor note:

Here in your validation class there's this comment. 


// Temporarily 0 = success, 1 = error



Which is fine. You don't want to use a boolean because you'll be adding more status codes in the future. Cool! But you shouldn't be hard coding the error code numbers. This is what enums are for. 

enum ValidationStatus {Success,GenericError}

// Check if user input was empty
public object inputNullCheck(string input)
{
    if (input != "")
    {
        this.ErrorCode = ValidationStatus.Success;


At this point, it would be better to remove this code


       this.ErrorName = "Success";
       this.ErrorMessage = "Valid input received";



And create a class that manages what Message to return based off of the value of the ValidationStatus passed into its constructor. 

Reducing the above code to

    if (input != "")
    {
        return new ValidationResult(ValidationStatus.Success);