When a new question is asked, then after how much time the "Start a Bounty" link appears?
Some time it appears immediately after asking a question. I recently asked a question for which I didn't see a link for that question.
start bounty option is made available 2 days after question was asked.
How do I start a bounty? When can I start a bounty?
A bounty can be started on a question two days after the question was asked.
It's never available immediately.