I correspond with a bunch of cat caretaking people. There was an elderly gentleman who had a dozen or so cats and lived pretty much in squalor like your friend. He had to go into the hospital. While he was gone, a bunch of the cat ladies got together and cleaned his place (they were feeding the cats for him while he was in the hospital. While doing so, they discovered he did not have a bed, had been sleeping on a terrible couch. So they got him a bed too.
On the other hand:
His lifestyle (squalor) is not necessarily something you should change, he's been living like this all his life, so it shouldnt worry you so much, as long as he is eating good (bring him a meal a day?) and staying healthy and warm..
Get him hooked up with the meals on wheels people?