Yeah, Step37, hard. I haven't had to deal with that in my own family (there was stuff at two points, but in both instances it all got sorted). Some of my work was in the home of hoarders, though, and it was intense. I can't imagine knowing I'd ultimately be responsible for what you're describing -that's a lot of square footage.
Are family members always handed that task? Or only if the property is willed to you?
I also watched two boyfriends return to super intense clutter (etc) when our relationships ended. I was a bit thrown to realize my presence and activity had kept things well in check, and very sad to realize how difficult it was for them to manage things independently (they are both very happy, however, so it hasn't actually hurt them! they're not concerned with managing things, that was only my schtick -they love the stuff, the more piles the better). I was surprised and perplexed: How does such an intense change in environment happen, and so fast, even with the smartest people and the best of intentions?
I wouldn't mind doing a total clean up over a few years so long as I weren't also working full-time. That would be too much! But hopefully if the garbage is willed to a person, the property underneath it also is, and one could FIRE and take the time to clean it up, or take out some equity and hire someone to. But I love cleaning so to me that's kinda dreamy. Maybe I'll come help you!!!