There are 5-7 years old second-hand servers that really do the job very well for what you need. Even with dual power supply
Discussion
I had rack mount servers in my house for many many years. I don't need or want that.
Then I misunderstood. If you are looking for a cheap option, I have set up raid storage with an old laptop, using both sata ports. With the added bonus of the battery, which saves you from power outages.
In fact I have a node just like this 🙂