JSFiddle - React, Tailwind, and code Playground

HTML

<div id="real-estate-edit" tabindex="-1" role="dialog" aria-labelledby="modal-responsive-label" aria-hidden="true" class="modal fade">
        <div class="modal-dialog">
            <div class="modal-content">
                <div class="modal-header modal-header-primary">
                    <button type="button" data-dismiss="modal" aria-hidden="true" class="close">&times;</button>
                    <h4 id="modal-responsive-label" class="modal-title"></h4>
                </div>
<div class="modal-body">
            <div class="col-md-6">
                <div class="mbm"><label class="control-label">Status</label>
                    <select id="ClientRealEstate_Status">
                        <option>Own</option>
                        <option>Mortgage</option>
                    </select>
                </div>
            </div>
        </div>
        <div class="row outstanding" style="display: none;">
            <div class="col-md-6"></div>
            <div class="col-md-6">
                <label class="control-label">Outstanding</label><div class="input-group"></div>
            </div>
        </div>
        
    </div>
<div class="modal-footer">
                        <button type="button" data-dismiss="modal" class="btn btn-default">Close</button>
                        <button type="submit" class="btn btn-primary">Save changes</button>
                    </div>
            </div>
        </div>
    </div>

JavaScript

$("#ClientRealEstate_Status").on("change", function () {
        CheckRealEstateStatus();
    });

    function CheckRealEstateStatus() {
        var ddl = $("#ClientRealEstate_Status");
        // alert(ddl.val());
        if ($(ddl).val() == "Mortgage") {
            $(".outstanding").show();
        }
        else {
            $(".outstanding").hide();
        }
    }