One of the most popular ways to get cheap HDD space is to buy external hard drives and “shuck” the drive out of them.
The point is to do this shucking cleanly, so that if you have send it for warranty recall you can put it back in the enclosure.
Before doing the shuck be sure to run somekind of a stress test for few days so you know that it doesn’t fail immediately.
I used the preclear plugin in Unraid for this.