81 year old Mom has allowed my only sibling to move in with her again. How do I find a safe balance?

Invoke your POA.. Make sure your Mom can not financially support him.. This may mean you have to be there for your Mom more but will stop the financial abuse your brother is inflicting on your Mom..

Just remember if she needs medicare in the future she will have to explain all her back expenditures...

Whodathunk reminded me of an option for you. You can call Adult protective services and report the situation if he is doing wrong. Since you have total POA - protect all her assets and stop cleaning the house. If he misbehaves call Adult protective services. Personally, I would inform him of it and let it play out. As long as your mom is safe and taken care of, of course.

My 65yr. brother was in jail for 14yrs. for DUI's and had been in and out through his life. I cared for my Dad up 'till he died in my arms. He had always worried to me about what would happen when Edward was released. I stayed on here after he passed to care for and keep company my Mom. It came time that he was going to be released, and Mom agreed to letting him come live with us. I continued to cook and clean as he assumed the role of needing to be cared for also and pushed it to the point of complaining constantly to my Mom untile I had enough and moved back home. To make a long story short he abused her to the point that Senior investigated and wanted to charge him,but she wouldn't. And when she finnaly got him out, she discovered he ripped her off to an unbelieveable extent, he even broke the seal on my Dad's ashes. Bottom line people don't change, past behavior predicts future behavior. My Mom still has not gotten over being violated by her own.