A mid-range gaming build without the GPU is capable of running a full saas stack for a small company let alone an individual.

https://pcmasterrace.org/builds

Depends on what you want to do with it. To start any old free PC that you can find online is going to work for experimenting with it.

If you plan to run 24/7, buy some proper fans and undervolt/set power limits to CPU and you will be saving with noise and electricity.

n150