Updates for v3 are paid only? There was this "one time fee" mantra overall and now I read 
https://craftcms.com/news/dot-all-2017-announcements

They will charge additionally on yearly base?
Does this include any update and security updates as well?
Ever since Craft 1 launched in 2013, purchasing a Craft license (Client or Pro editions) has included free updates – even major releases, which means that your current Craft 2 site will be eligible for a free upgrade to Craft 3 once it launches in April 2018.

With the release of Craft 3, this will change: in order for your site to stay updated, you'll have to renew your Client or Pro license yearly, for a reduced fee ($39/year for Client edition, $59/year for Pro). If you opt out of renewing after the first year, you won't receive any further updates, but your license will still be valid and your site will still work.

Note that the yearly fee does not apply to any existing licenses, which will continue to receive free updates indefinitely.

Source: https://craftcms.com/news/dot-all-2017-announcements