My mother didn't start out as a hoarder (probably because she always had a maid who helped keep things tidy, but we always had the house full - but liveable), but as her mental illness progressed, within 2 years that house became a pandemonium. She definitely had some sort of shopping compulsion, some things didn't even make any sense - like paying for expensive frames in blank canvases.

To picture it, when I went back home while she was sectioned (the only way I gained access) I couldn't sleep there, it was that full. I ended up sleeping in my grandma for a few days while cleaning it up.

Then my brother and I did a big clean up and sorting out and we ended up filling about 3 containers like these and moving an insane amount of junk to the garage. IIRC, we counted about 200 potted plants in the living room and balcony - in a not particularly big flat.

We always clean up when we go back home and she always hates it. Last time she locked herself in the bedroom for 3 days because she was so furious at us.