Make customers vendors FES

plugin.php

<?php
add_action( 'edd_complete_purchase', 'fes_add_buyers_as_vendors', 10, 1 );
function fes_add_buyers_as_vendors( $payment_id ){
	$customer_id    = edd_get_payment_customer_id( $payment_id );
	$db_user 	= new FES_DB_Vendors();

	if ( $db_user->exists( 'id', $customer_id ) {
		return;
	}

	// create user
	$user = new WP_User( $customer->id );
        // note: Insert as pending then set to approved right underneath.
	$db_user->add( array(
		'user_id'        => $user->ID,
		'email'          => $user->user_email,
		'username'       => $user->user_login,
		'name'           => $user->display_name,
		'product_count'  => 0,
		'sales_count'	 => 0,
		'sales_value'	 => 0.00,
		'status'	 => 'pending',
		'notes'          => '',
		'date_created'   => date( 'Y-m-d H:i:s' ),
	) );
	
	// set to approved
     $vendor  = new FES_Vendor( $user->ID, true );
    	$vendor->change_status( 'approved', false );
}


// Alternatively
add_action( 'edd_complete_purchase', 'fes_add_buyers_as_vendors', 10, 1 );
function fes_add_buyers_as_vendors( $payment_id ){
	$user_id    = edd_get_payment_customer_id( $payment_id );
	$vendor = EDD_FES()->vendors->make_user_vendor( $user_id );
	// set to approved
     $vendor  = new FES_Vendor( $user_id, true );
    	$vendor->change_status( 'approved', false );
}