Google Colab is basically like Google Doc is for Microsoft Office as it is for Jupyter Notebook. It basically lets you create, edit and host Jupyter Notebook in the cloud.
Google Colab for Training Models
Training is essentially free and easy on Google Colab. You have access to both GPU and TPU. Though the free version can lose temporary variables, files in the home directory, because it refreshes every 12 hours or less. There are ways to save and download the files to avoid such catastrophe.