Yes - in the process of doing this right now (I can hear the builders)! I am an only child and DM has moved in - proceeds of her house paid the deposit and DH and I raised the mortgage.
Won't lie to you - it's been hard. At times I want to strangle my mother and she has, in her (not so) old age started to become a whiny hypochondriac which is infuriating.
That said, DH and I would have had no hope of getting on the ladder before an inheritance without doing this and now that we can see the light at the end of the tunnel it's worth it.
DM has one side of downstairs as an annexe (bedroom with en-suite, kitchen and living room). We can easily change this set up once the house is just ours - morbid I know - but worth considering.
It's handy having built-in dog/child care, which we've never had help with before. It means DH and I can both work full time and build our careers.
DC have been very good with it. DS1 is 17 so already looking at moving out in the next few years.
In terms of the financials - offically, DM gifted us/me the entirety of the deposit and we are the sole owners of the property. She has no legal entitlement to anything, which is a huge trust on her part. DH and I are solid though, and as an only child there are no other parties to consider. You will need solid legal advice to make it work for your individual circumstances. DM is only in her 60s, so no care required yet, thankfully. As mentioned, it would fall to me anyway.
If I die, they can sort it out amongst themselves - I won't care. I'll be dead. If she hates it, tough shit tbh. It was her idea and we're the ones who gave up independence at her behest, not the other way round.