With Dynamics CRM Online 2013, you start out with one production instance and 5 GB of storage.
We offer a free non-production instance if your CRM subscription includes 25 or more professional USLs (User Subscription Licenses). A non-production instance is an add-on instance that is separate from your production instance. All users in your production instances are also users in all your non-production instances, unless you want to restrict the access using a security group.
You can always buy non-production instances. Non-production instances are roughly 70% cheaper than production instances. For the most up to date pricing and licensing information, please refer to the Microsoft Dynamics CRM Online pricing and licensing guide here
We also offer free storage. For every increment of 20 professional USLs, you will be granted 2.5 GB of free storage until your storage capacity reaches 50 GB. You can always buy extra storage at roughly $10 GB/month.
So how do you know if you been granted a free non production instance, free storage and how to buy more? All these questions and more are answered in this blog post from the CRM Team