Beware ! If the time comes and your Mum does need to go into a home the council WILL, illegally, try to get you to sell the house to pay care fees. They
try this on all the time now , just look back at some of the threads on AB !
When they try it with you (and they will ) you have to refuse and insist that your Mum gets 100% funding. The value of half a house with a tenant (you) who has the right to live there for life is effectively zero so your Mums assets are nil and she qualifies for 100% funding. When and if the time comes you have to refuse to pay anything and insist she gets the 100% funding she is entitled to. Once they realise you are not going to pay and that you know the law they will back down.
My brother is the senior housing finance controller for a large London council and he has told me that the officers will do this and that they have to back down once they meet up with someone who knows the law and stands up to them. But the council officer are told they have to try to 'persuade' relatives to fund care and save the council many thousands of £s. Remember the cheapest care homes start at over £550 a week ! and it can go to over £2000 a week , no house sale is going to fund that for long !