Budget-friendly RAID Array for 15TB+ video storage on Mac?

I'd love some advice from the data-hoarding hivemind! I currently have a ton of video projects and footage sitting on random hard drives around my office—about 15TB worth.

Since Black Friday is around the corner, I figure it's a good time to set up a RAID 5 enclosure instead as "cold storage" for my finished projects.

I'd likely need 20-25TB to start, but it'd be great if I could add new disks down the line to keep it somewhat future-proof. Since it's storage, speed is less of a concern than cost and storage space. I'd love to keep everything around $1k or below if at all possible. It doesn't need to be network-attached or anything and if it makes a difference, I'm on Mac.

Anybody care to point me in the right direction? I won't pretend I'm techy, this is not my area of expertise so I'd be incredibly grateful for any input or advice!