If I want to update my website theme do i need to pay extra
No - assuming you buy the theme from Themeforest then you get lifetime updates for as long as they become avalaible.
Envato market items update download free for lifetime .
You can use Envato Market WordPress Plugin to get auto update features. This plugin helps customers receive updates to their premium wordpress Themes & Plugins purchased through Envato Market (ThemeForest & CodeCanyon).
you can download the plugin from here:
Using this Envato Market WordPress Plugin you will see:
- Latest version (need to update version) number
- Details view option for the latest version
otherwise you can download the update version from Envato Market Downloads page and update manually using ftp.
Note: Better to keep a full backup before doing the update.