Comments based on assumptions due to post-count:

The parking brake on these cars is an internal drum on the rears, so if the noise is from the back, it may be there. Or it may be something like a broken spring inside the rotor. They're not too complicated, but can be a rusted dirty mess depending on location.

The pads on the brakes are easy-as-pie to remove and check. But the calipers trap a lot of dust and dirt. If the pads are dragging just a bit, you can thoroughly clean the calipers, use hi-temp brake grease on the sides to lube them.

You may get various input about collapsed brake lines. Maybe, maybe not.

Since you just got the car a few weeks ago, a brake service to include a fluid change may be in order anyway if the fluid's dark. Plenty of info here on those topics.

Grinding noise could also be a bearing. Another not too difficult task with plenty of info.