Can I install Windows 10 as a download (new download purchase) in Boot Camp?

I am thinking about buying an iMac, but I don't have a copy of Windows 10 (I want to have a partition for Windows in order to install MS Office products that I will un-license from my outgoing PC), so I plan on buying Windows 10. The purchase will be a download, so I need to know if I will be able to (and how to do so) execute the purchase and then download Windows 10 in Boot Camp (no disk or other media for installation)?