Is there any good reason to avoid a used SuperMicro server for my build?

My old Windows Home Server is getting dangerously old at this point and I really need to hop on building something better. As I'm shopping for parts for a FreeNAS build I'm finding that large multi-bay cases from the likes of Norco and SuperMicro cost $300-500 just for the bare metal and drive cages (not a spec of hardware inside). Yet on eBay and CL you can find used SuperMicro servers with all the hardware inside for $300-500.

Is there any good reason to avoid buying a used...

Is there any good reason to avoid a used SuperMicro server for my build?