If my elderly mother with dementia comes to live with us, would my husband lose his benefits or my mother lose her invalidity pension?

You'll have to check with the sources of income. It is possible, as some of the benefits are (unfairly, in my opinion) based on household income. Please chcek with both sources before making a final decision so that you are can make an educated decision. It's very sad that this even must be considered, but you want to go into this with your eyes open.

Take care,
Carol