You've got a few ways to do this but I'd argue that this is the easiest way:

MVC will by default bundle the jquery.validate javascript library into your page. Since you are already marking the field with the [Required] attribute, the Html.EditorFor will bind the correct attributes into your HTML for you so that validation can happen as necessary.

To make your current logic work with the smallest changes, you could add a <form> tag around your input field(s). I think you need this for the validate method to work out of the box. Then your javascript would change to something like this:

$('#Overview_Title').change(function() {

if ($(this).valid()) {

  // do your stuff

  }

else {

  // error message displayed automatically. don't need to do anything here unless you want to

  }

});

This would allow you to use the Required attribute to set your error message text and your ValidationMessageFor should display the error message without any extra effort on your part.

Check out this plunkr as a proof of concept: http://plnkr.co/edit/ip04s3dOPqI9YNKRCRDZ?p=preview

EDIT

I'm not positive I understand your follow-up question. But if you wanted to add a rule to a field dynamically, you could do something along these lines:

$( #someinput ).rules( add, {

 required: true,

 messages: {

 required: a value is required to save changes

 }

});

You could add rules that aren't reflected server side by doing something like this. Then you could validate that input in the same way.