We were in a different situation as we pooled resources with my parents and bought a house where we could live together. In the early days we were the beneficiaries of childcare provided by my mum as our children were young. After my dad died we had many years during which mum lived an independent life alongside us. However, as she became more frail, we took on more caring responsibilities, ultimately being her full time carers for her final six months. I don’t regret it but I am aware that we had a fairly easy time of it because Mum remained in quite good health until those last six months, at which point she declined fairly rapidly. So that period of full time caring was relatively short.
Having said that, it was probably the years running up to that final demise that were harder to navigate- we reached a point when we couldn’t reliably leave her at home alone for any length of time, so family holidays were a no go (this coincided with COVID so made little difference to us). We tried to go away for a weekend, and my brother came to look after mum - DB had no clue how to care for her and we ended up coming home early.
I’d strongly recommend looking at attendance allowance - by the time we got it, Mum was due the top level. You’ll inevitably quickly get drawn into managing financial decisions and medical appointments, and it’s quite surprising how those little things mount up.
I don’t envy you trying to make this work in your Mum’s house - where she is presumably used to having all the space to herself. We found it enormously helpful to each have our own living space. If you can create that within the house I would strongly recommend it.
As Mum deteriorated, we had to keep tweaking the arrangements that we had in place - it’s like raising a child in reverse with new ‘milestones’ such as no longer using the stairs or needing help with personal care. You need to be prepared to adapt and your Mum needs to adapt too. Will your DH get involved in her care? My DH was used to caring as he had a disabled sibling and so he was very actively involved in caring for Mum, but still a lot fell to me. I struggle to imagine how I’d have coped without DH’s support so I hope you have the same.
I will say that I found it rewarding and I am glad we were able to care for Mum at home up until her death. Thankfully her deterioration was mostly physical and she remained mentally healthy barring a few senile moments. If she had lost mental capacity it would have been much more difficult.
Good luck and I hope it all works out for you.