Plans
Start free. Move up when you need more.
On a paid plan the allowance goes down with the text the model reads and writes, not with a count of questions: used heavily it can run out before the period ends, and it refills when the subscription renews.
You can stop whenever you like: the plan ends that day, and the share of your payment for the allowance you have not used goes back to your card, less the card processing fee.
Any tax that applies where you live is worked out on the payment page, before you pay.