<div class="panel-group" id="rooms-information">
  <div class="panel panel-default">
    <div class="panel-heading">
      ...
    </div>
    <div class="panel-collapse collapse">
      <div id="rooms-information1" class="panel-body">
        <div class="buttons col-md-4">
        </div>
      </div>
    </div>
  </div>

  <div class="panel panel-default">
    <div class="panel-heading">
      ...
    </div>
    <div class="panel-collapse collapse">
      <div id="rooms-information2" class="panel-body">
        <div class="buttons col-md-4">
        </div>
        <div class="buttons col-md-4">
        </div>
      </div>
    </div>
  </div>
  <div class="panel panel-default">
    <div class="panel-heading">
      ...
    </div>
    <div class="panel-collapse collapse">
      <div id="rooms-information3" class="panel-body">

      </div>
    </div>
  </div>
</div>

$("#rooms-information").ready(function() {
  $("#rooms-information .panel-default .panel-body").each(function() {
    var id = $(this).attr('id');
    var countButton = $("#" + id + " .button").length;
    if (countButton == 0) {
      $("#" + id).append("<p>Empty</p>");
    }
  });
});