Hello Joao,
To get started with Azure HDInsight (Hadoop) you can see the pricing table below:
HDInsight pricing
https://azure.microsoft.com/en-ca/pricing/details/hdinsight/
You can also speak to a Sales Specialist about this product here:
Get one-on-one guidance on Azure pricing
https://azure.microsoft.com/en-ca/pricing/contact/#contact-sales
You will need to upgrade to a pay-as-you-go account to use Azure HDInsight services unless you have some free Azure credits remaining.
If this is helpful please accept answer.