I bought a used desktop with 4 SATA ports. Has i5 7th gen and currently 5 TB and an 500GB SSD and has max ram of 64GB. I guess the HDD are not included in the price?
I’m not sure what your software requirements are but if you go the DIY route a desktop works. I made the BIOS auto turn on on power restored and have services start on startup so it gives the server feeling.
Bonus is that you can use it as a gaming server and upgrade the components easily for a while depending on the motherboard.