eBay hardware buying advice?

I am hoping the great folks on the forum here can give us some pointers/advice as far as buying used enterprise hardware off eBay. Or someplace else if there are any good recommendations.

I have worked in IT for almost 20 years and bought many servers so it isn’t anything new to me on looking at specs, understanding them, etc. But I’ve always bought new for work and always with the understanding that so as long as the hardware was in service we would either have it under warranty or add it to a service contract. Neither of which I am as concerned about, nor want to pay for.

I am looking more for advice on the little things. Like pluses and caveats with hardware I maybe have no experience with. Or things to make sure are included or things to not worry about.

Based on my initial looking I think I would be leaning towards a SuperMicro or Dell server. Prices and availability seem to be decent. HPE might be an option, but getting firmware makes me wary. In my professional life I’ve used HPE for ages, but I want to make sure I can get the firmware easily even if the device isn’t under warranty or a support contract. I have some Dell experience from 10+ years ago. It was ok from what I remember, but quite a few components were cheap in quality. I have zero experience with SuperMicro.

So please share any advice you have. Things that aren’t obvious in the listings like how good or bad the remote management is. Or how easy or hard it is to update the firmware. Especially when running an OS that isn’t Windows. Items to make sure are included or not to worry about. Things like disk caddies, rails, bezels, etc.

Appreciate the insights and hopefully it will help others. Also if there is already a thread about this please point me there. I searched but found nothing. Thanks!