I have had my dad living with us for the past year. He is 85 and has dementia. It is really tough, we had an enclosed dining room downstairs which was my husband's home office, and he had to give that up to be my dad's bedroom.
It is very cramped, there are 5 of us now and my dad has no awareness of other people's space, personal belongings or boundaries.
We have to hide things constantly and I recently got a lock put on my bedroom door after he entered my room during the night ranting and gave me a real scare.
This is just my experience but it seems social services are less willing to provide any help to an elderly person living with family even if the family member like me is disabled and not able to do certain aspects of the care.
I feel like it will be a real battle to get help if he can no longer wash or toilet himself.
However it is likely to be a better experience if you go into it buying a suitable home with enough space for everyone.
You would first have to really look into both the likelihood, timing and financial implications of your mum going into a care home should this become necessary.
I believe people can be forced to sell their home unless a spouse, their own child if over 60 or disabled dependant person lives there, and if you have bought a home together then you could be at risk of homelessness.
Even if it was put in just your name, if they find out (and they do really dive into a persons finances going back years) that your mum contributed, they can still seize your home.
So please do look into that thoroughly, maybe get some professional advice.
Buying or converting two adjoining but legally separate units and knocking a door through may be an option, then one is legally yours and one hers, so at least yours is protected from seizure for care home fees.
Regarding my decision we didn't do it out of choice, my dad was no longer safe living alone and we were unwilling to entertain the idea of a nursing home both for his sake and to protect everything he has worked his whole life for being seized by the state instead of being able to be passed on to my children.