Brent wants to create a central network attached storage that can cater both OS X and Windows. Leo says a NAS devices are great for that purpose. Western Digital is a basic NAS that can do the job. More advanced products like Synology offer advanced features that can be advantageous.
But there's a third option. It's called The Transporter. And it's like DropBox, except Brent would own the storage, not a third party service. It's like a personal NAS storage for the cloud and can even work as a great backup option. It works with any USB hard drive he'd have lying around. He can also get a router that has a USB plugin for an external hard drive and he can plug it in that way as well.