If you need ~20TB or less of space, I’d suggest that you just add an extra HDD to any computer you already have. You can get that in a single drive for a few hundred dollars US without doing anything particularly special. I can find various 16TB 3.5" HDDs being promoted around $330-ish USD right now with ~30 seconds of looking; you might be able to get better $/TB if you spend longer looking than I did.
I’m sorry. Your purpose is to pass the butter. Through your colon.