I have seen some REALLY cheap used server stuff on Amazon, so if you don't already have the computer, then these might be better options.
Examples:
More Space Efficient (Also has cool mini display thing. I am currently looking at a similar one with dual 6 core CPUs): https://www.amazon.com/dp/B077H43B8D/ref=sspa_dk_detail_0?psc=1&pd_rd_i=B077H43B8D&pd_rd_wg=DcHcv&pd_rd_r=VHJ67F0WT3AYV0CWSCQD&pd_rd_w=gcjtP
More Storage: https://www.amazon.com/HP-ProLiant-DL380-G6-2xQuad-Core/dp/B00OGMGECQ/ref=sr_1_5?ie=UTF8&qid=1517371698&sr=8-5&keywords=server
Configure a custom one for cheap (I haven't ordered from this site, but it is trustworthy from what I have heard. I will probably order that dual 6-core CPU server here since it is from the same company that was on Amazon): https://techmikeny.com/
I would also like to mention that you should NOT use used hardware for anything that would be catastrophic if the server failed. Anything mission critical should be NEW!