Hi,
As mentioned in the prerequisites, you will need your own Azure subscription to complete the exercise.
For the Sentiment Analysis aspect you can use Pricing tier Free F0 (5K Transactions per 30 days), so no charge for that. For the Logic apps aspect you should select Consumption, which includes first 4,000 actions free, so if you only test with small number of Tweets there is no charge.
Additionally, the exercise uses Logic Apps Standard connector, which costs $0.000125 Per Call, so as above if you perform small number of tests the charge should be virtually zero.
After completing the exercise you should delete any resource group(s) you created and verify afterwards that the resource group was successfully deleted. This will delete the resources within to prevent unintended charges accruing.
Azure AI Language pricing
https://azure.microsoft.com/en-us/pricing/details/cognitive-services/language-service/
Logic Apps pricing
https://azure.microsoft.com/en-us/pricing/details/logic-apps/
Please click Accept Answer and upvote if the above was helpful.
Thanks.
-TP