To not want my MIL to move into our annexe

Ask your DH what his answer would be if you wanted your DP's to move into the annexe
This.

All adults should have a right to veto someone else moving into their home.

Men can do of course but statistics show that its overwhelming women who are expected to and taking on caring roles: https://www.ageuk.org.uk/our-impact/campaigning/care-in-crisis/breaking-point-report/

1. The majority of carers are women. Almost 6 in 10 (58%) of carers at the last Census (2011) were women. Caring falls particularly on women in their 40s, 50s and 60s, with 1 in 4 women aged 50-54 having caring responsibilities for older or disabled loved ones, compared to 1 in 6 men[5].

1. Women are also overrepresented in those providing ‘round the clock’ care, with 60% of those caring for over 50 hours a week being female[6].

1. As a result of women’s overrepresentation amongst carers, particularly those aged over 40, reductions in practical and financial support for carers and rising demand for unpaid care and support are likely to have a disproportionate effect on women and their employment prospects.

1. Increasingly parents are combining looking after young children with caring for older or disabled loved ones. Research from YouGov suggests that over 2.4 million people are already combining raising children with caring for older parents.[7] This is often called ‘sandwich caring’ or ‘dual caring’.

1. Research shows that women are more likely than men to be sandwich carers[8] and the peak age for sandwich caring is 40-49, slightly younger than the peak age for caring. However the impact on the ability to work is likely to mean that the retirement income of this group will is be significantly affected.

From government stats.

As someone who willingly had my much-loved Mum for the last few years of her life, I still wouldn’t recommend it, if there is an acceptable alternative. It nearly finished me off. Have you actually cared for an aging parent 24/7 for a number of years?

And no I don't mean care

You might not, but old age is relentless and insidious in its progress. My Mum was able to get herself to the loo with a frame, when she first came to us. By the time of her death, she had be helped on to the commode and assisted afterward, spoon fed, encouraged to drink and had a catheter, because of frequent UTIs. I couldn’t have done it for anyone else.

Edit: Oh, and I am the mother of sons and I have already told them I shall be perfectly happy in a home (the thought absolutely terrifies me), because I don’t want them to feel either trapped or guilt-ridden. I want them living their lives.

I really disagree with this comment. Many men take on caring roles.

Of course, OP might well, but it's not a given.

I’ve lived with my MIL and would tell every woman on earth DON’T DO IT NO MATTER HOW NICE YOU THINK THEY ARE.

My fil wants to live in our annex.

i told dh he could agree as a divorcee.

don’t buy a house with an annex.

What were your plans for the annexe?

And be under no illusions: it will end in caring. We ended up with both surviving parents (his and mine) around the corner from us and looking after them at the end of their lives, even with help, took a lot of work. The closer you are, the more you'll have to do.

Absolutely not in the circumstances.
Did he steer you to the house because of the annexe ?
It would be a deal breaker for me.

I had this conversation with my husband years ago. I didn't want to live with my own mum either, but I did make it clear to him that however much I loved his parents (and I really did), I wasn't going to say no to my mum (who would always have wanted to live with us) and then say yes to his. That really is only fair.

Your husband sounds like he needs a big wake up call on respect.

’No. You can barely be polite to my parents, but think it’s ok in return to consider your mother basically moving in to our family home? I don’t think our marriage could survive that much hypocrisy to be honest. That’s before you even get to the question of elder care and the use of the annexe. I do not want to live with extended family and I don’t think it will work for any of us, including MIL. No.’

Honestly the fact that he’s even got to the point of discussing rent would have me LIVID. And I’d be asking to see that eviction notice, because I think it’s rather suspicious timing.

Unfortunately I think you might be right, we will end up with a generation of stunted kidults who never flew the nest.
We will become like those backward countries where this is the norm.

A lot of people are going to have to rethink their views. Elderly population, lack of affordable housing. I think in the future we will have children who can't fly the nest and parents who, because of the expense and lack of care facilities, live with their children. In lots of countries this is the norm.

This.
If he won't tolerate your parents then you don't tolerate his parents.
The end.

I agree with this. Do not walk into this trap.

Yes, this is a big sign, frankly, of your boundaries being stepped way over. He can't be in a room or spend much time with your parents in law, however it's ok for his mother to virtually move in. Not OK.

you'll want a written contract that if she needs help then DH will have to do it

No no no..

We accepted money off the in laws towards a house once and never again I ended up selling and giving the money back!

Different situation but no way would I be buying that house.

Our house had a half finished ground floor annexe when we bought it. Due to my health, and as it turns out, my DH as well, we turned it into a ground floor master suite. Which sounds a lot posher than it actually is, but it really works well for us. And incidentally, stopped my mother thinking she would move in with us if her husband passes away before her.

My feelings are also clouded because my husband does not like my parents, which I find very difficult. It is a very long story, but I don’t agree with his views about my parents. I find it hard to swallow that he can barely stand being in the same room as my parents, but I am being asked to consider having his mother live in our annexe.

No, for this reason alone. The resentment will eat away at you and I wouldn't blame you one bit.
That's before you start thinking about all the ways her care will become your problem.
I would have no qualms in telling him this either.

I would rather pull out of buying the house than let her move in. It’s a no from me

Very possibly, yes
I was only thinking of the rows it might cause if OP's seen to scotch a carefully made plan, but of course better one row now than endless ones in future if the demands ramp up

I absolutely would not agree to this. For certain you will be providing for any care needs. With medication and care many people live into their 90’s with ever increasing care needs. If you end up with all that you will have no life.
Do not buy that house, your dh wants the annexe for his dm.

No way would I agree to this. I've done elderly care for relatives twice now and I wouldnt advise anyone to do it. It starts small and then gets more and more exhausting and demanding as time goes on. I almost had a nervous breakdown trying to juggle caring/assisting with a full time job, my own kids and balancing my own needs. My mental health still hasn't fully recovered and I would never take it on ever again. I would advise anyone to think very carefully about this because unless you've been there, you have no idea how much it affects you.

No way, she already annoys you, that will be 10 times worse when she's in the annex.

If you think you will end up her carer sounds like your DH already has some expectations of you?

Nip this in the bud now.