I was in the exact same situation with my parents. They got in way too deep with an AMO and ended up losing the house I was raised in. I was the only one of my family in a position to help my parents at the time. My parents moved in with me but under some conditions. 1-NO BUSINESS DEALINGS WITH AMWAY. No money spent on the business at all. If they can’t afford rent, they cannot afford their “business” and my dime was not paying for it. Their AMO was not to call the house or come into my house. I made them have a plan to get solvent again and budget to get back on their feet. It was tough and there were times they were not happy with me but what could they do, I held all the cards.
Anyway, they did what they needed to and helped themselves up. They are doing much better now so I am thankful. Just stay strong and keep to the rules. Letting your son move in if he needs help is not your job if he will not take steps to help himself, but if he is willing to do what he needs to, I would help him as long as he understands that. Good Luck and keep in touch with us.