No license is required for Studio Pro.  You can develop both locally with Studio Pro, or deploy the app to a free tier application.  When running locally, Studio Pro will stand up your localhost environment with everything you need.  If you want to run this in the cloud, you can publish to a free app: https://docs.mendix.com/developerportal/deploy/mendix-cloud-deploy/#free-app.  

I would recommend following a few learning paths if you are just getting started. 

You can use Mendix Studio Pro without a license in the sandbox environment.

thanks Luke but i’am discovering Mendix since this morning, what do you mean by Sandbox?