BuddyPress.org

I think ‘bp_init’ is the wrong hook.. Try using ‘bp_core_signup_user’

function save_wc_address() {
 	if ( wp_verify_nonce( $_POST['bp_settings_general'] ) ){		

		$user_id = sanitize_text_field( $_POST['user_id'] );

		//sanitize input data
		$billing_phone = sanitize_text_field( $_POST['billing_phone'] );

		//update user meta
		update_user_meta( $user_id, 'billing_phone', $billing_phone);

	}
 }
 add_action( 'bp_core_signup_user', 'save_wc_address');

source:
http://wordpress.stackexchange.com/questions/160475/how-to-increase-password-requirements-for-registration