Check out your local computer shops? There's lots of old office SFFs floating on second hand market, and they upgradable. And in terms of usage, they're probably been mostly internet machines

 

Our company alone has around 5,000 of these thingies in use and they are replaced roughly every 3 years. Most larger companies rely on hosting platforms with virtualized Windows clients for scalability reasons.

This means that theses little machines are really just peepholes on the server in the data center. They themselves have hardly been used (only remote desktop), never got hot because that task isn't demanding in amy form and will easily last > 5 years.
I would never buy one new.

The second-hand market is full of hundreds of thousands of these parts, just like @Legotron says.

 

Why I like the HP series,
1. overbuilt for purpose (office machine) 4 usb 3 ports (good for external storage devices)
4 usb 2 ports, good for keyboards and other midi over usb devices - also has ps2 keyboard/mouse so can free up usb ports by using ps2.
2. 2 sata ports and one pcie slot
3. external power supply like a laptop machine so much cooler internal temps and less rf interference as power brick can be
relocated away from audio gear.
4. dual monitor support
5. easy to work on, 1 thumb screw gets the top off and bob's yer uncle.
I run arturia v collection9, ableton 10 and Reaper and Battery 3 on it no problems.

I've paid more for a guitar case than I have for this computer all kitted out.

Is it cutting edge? no
Is it going to run windows 13? no
is it connected to the internet? no

Is it reliable, cheap and easy to upgrade? yes.

Is it for everyone? no, but its a cheap way to find out what your needs are and can always be used as a backup machine
for testing software or running virtual machine emulations

 

So take this with a grain of salt, because I'm no expert producer or musician or anything, and literally just started the hobby around this time last year but for the first 6-8 months I used FL Studio on an HP EliteDesk G2 800 mini, with 16gb of RAM. It's an i5-6600T - which is a 2.8GHz quad-core cpu, no hyperthreading so just the 4 cores. Of course there is an SSD in it. I actually got it for free, I actually have two of them but I had bout a Arturia MiniLab 3 which of course came with Analog Lab V which is resource hog. I actually bought a computer around the 6-8 mark with the intent of producing on it but this HP isn't bad. I'm typing on it right now. I use it as my "workstation" (because my production pc doesnt do anything but music) and run stuff like Adobe Photoshop, Illustrator, Dreamweaver, stuff like that. I also run AudioGridder on this one and the other one (it runs my TV and acts as a file server/hosts my private large language model i use to chat with my documents), the setup on that one is identical. lol I'm a nerd I use like 4 computers at once

Anyway I would say this line is worth looking at, Dell has a mini system line too that probably some decent machines, if your dead set on a mini-machine. I honestly thought about pairing this with spacedesk, which lets me use an old android tablet as a wireless monitor, and my FL Key 37 to have like a portable, headless FL system thing but I don't go places near enough to do all that.

 

Nob here.
I found a HP ELITEDESK 800 G4 i7-8700 with 64GB RAM & 1TB SSD + 6TB HD on a very low price.
Can I use it CUBASE pro-11. I use Fabfilter plugins and few waves too and liquidsoniq's cinematic room. Some CSS and spitfire libraries all located on external drive.

 

If you own it, you can use it for whatever you want to. You'll never know until you try. No one ever became great by asking for permission. Enjoy your new machine...

 

Yeah, that is a great machine, how much does it cost?

 

Bit late, Got it for $350. Happy new year

 

Happy New Year brother and have a blast making music on that lovely machine, such an great deal!