Usually labeled as P series.
This is how I do my home system, Dell r710xd I believe. I bought it used via craigslist and I think it came from the local power company. In the States we have government surplus sites that have stuff cheap.
You can mount a rack mount system vertically on the side of the wall, hanging down with a couple of shelf brackets.
I disagree! They can be great options, inexpensive and reliable. My current home server is a Dell r620 with xeon CPUs, 64gbs of RAM, and 2 terabytes storage in raid 5. It serves several vms, a mix of Windows and Linux. More than enough for many home set ups. Boots the os off a 16gb flash card. Cost me $185. Thing has been a tank.
I bought two short L brackets from home Depot, and have it hanging flat against the wall. It’s been fabulous.