Addictions are really a mental health issue, and most mental health issues, especially addiction, these days are linked to diet & one's microbiome - "The stomach produces 90% of our serotonin and 50% of our dopamine, both neurotransmitters that make us feel good and “normal”, in addition to performing many functions that lead to improved mental and physical health. The typical American diet consists of a lot of processed foods, and people with addiction sometimes don’t eat much at all. Both lead to an insufficient amount of good bacteria in the stomach, which means the brain and body don’t get what they need in multiple areas." -
https://cornercanyonhc.com/gut-brain-connection/ Here is a list of evidence based foods for depression -
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6147775/.
Some healthy, easy to prepare groceries and home cooked meals might help. He might be able to get food from a food bank or pantry. Whole foods with lots of plants might help. If you want to go further, offering to pay for nutrition testing, gut testing, or a functional medicine exam could help, and certainly wouldn't hurt. Many older people are low in vitamin D, which can impact seratonin levels. Also just getting your friend out in nature and going for a walk might help with the depression he likely has, instead of getting his fix with spending.
Hiring a CPA or tax attorney to sort out the back taxes would help with applying for government programs. He'd probably also need the taxes sorted out to see if he could file for bankruptcy. Some states have homestead laws. A bankruptcy attorney might also help on this front.
Our local senior center has people on staff to help with senior counseling and senior budgeting. Your city or county likely have a similar office you can contact on his behalf. They may have some free mental health counseling. Unless he has much more debts than you know about, it is not too late for him now to have a comfortable retirement between his home equity, SS and possibly other government assistance programs. Our government and local senior center have many senior programs like free transportation, free meals and activities, help with utilities, and some are not asset based.
You could also do a budget showing his trajectory now and one with a roadmap and lifestyle (especially the rented room instead of the house) for financial solvency. I'd put this all in a written plan, maybe step by step action items and a goal list, you can hand to him to think about and refer to. I have tried some, though not all, of this stuff with family members and what I have tried has worked. I have friend and a couple of relatives I am concerned may end up homeless through addiction spending so I've given this some thought and this is what I think I can do to help them.
And of course I learned the hard way not to just give them money as it will go to totally insane consumer items instead of necessities. Good luck, your friend is lucky to have you and your husband for friends.