Not OP, but I have an R620 running in my garage I use for self hosting. It has 12 cores (Intel Xeon E5-2665), 96GB of RAM, 10x2.5" drive bays (came empty). The SSDs I use I shuck out of old external USB drives.

Together with a full standing rack on wheels, I bought them for $600 cash (plus U-Haul rental to get it home).

My trick is craigslist in a city with datacenters (PHX). There are resellers here who buy used hardware from local datacenters and resell them to smaller businesses. I've had it running 24x7 for almost 3 years now and it is still going strong.

https://www.reddit.com/r/homelab/ has some good references for acquiring hardware for a home lab setup.