JSFiddle - React, Tailwind, and code Playground

HTML

<div class="pricing-levels-3">
          <p><strong>Which level would you like? (Select 3 Levels)</strong></p>
          <input class="single"type="checkbox" name="vehicle" value="Bike">Level 1<br>
          <input class="single" type="checkbox" name="vehicle" value="Bike">Level 2<br>
          <input class="single" type="checkbox" name="vehicle" value="Bike">Level 3<br>
          <input class="single" type="checkbox" name="vehicle" value="Bike">Level 4<br>
          <input class="single" type="checkbox" name="vehicle" value="Bike">Level 5<br>
          <input class="single" type="checkbox" name="vehicle" value="Bike">Level 6<br>
          <input class="single" type="checkbox" name="vehicle" value="Bike">Level 7<br>
              <button type="submit" id="submit">Button</button>
        </div>

JavaScript

var limit = 5;
$('#submit').prop("disabled", true);
$('input.single').on('change', function(evt) {
   if($('input.single:checked').length == limit) $('#submit').prop("disabled", false);
   else $('#submit').prop("disabled", true);
});