I have a ReadyNas NV+ v1 in mint condition. I'm retiring it because I moved my back-ups to Thunderbolt direct connection Drobo.
The ReadyNas has the most recent updated firmware and is gigabit ethernet and Time Machine capable. It has 4 drive bays that can accept up to 4X4TB drives in Raid-X configuration.
It has three USB 2.0 ports to attached external drives and/or printers.
$250 or best offer + shipping and insurance.