Thirty Five years ago, my brother in law had one of these built for his recently widowed mother in law, who seemed unable to live by herself. Used the money from sale of her small flat to pay for this.
This lady, who seemed so very physical fragile lived for a further 33 years. Over that time, they several times had to move home, and on each occasion then had to spend a lot of extra money building an annexe for her.
By the time of their last move, when they were trying to downsize, they could not afford to do this again, so she had to live in with them. She was already suffering from dementia, and just could not understand why she could not 'go home'. Within less than six months of moving there, her daughter was at the point of having a total nervous breakdown with trying to look after her extremely distressed mother who was causing so many problems. She was finally found a place in a home, and stayed there for a further couple of years before she died.
It has cost them of hundreds of thousands of pounds over these years, and they now say that if they had any idea they would not have done it in the first place.