Start coding sooner with a virtual machine prepped for Windows 10 development. It has the latest versions of Windows, the developer tools, SDKs, and samples ready to go.
If you just want to try out Windows 10 and UWP, use the free evaluation version of the VMs. This will expire after a pre-determined amount of time. However, if you want a VM that won't expire, choose the licensed version and add your Windows license key. Don't already have one? Buy a new Windows 10 Pro license (EN-US only).