To be fed up with in laws here all the time and hubby moving his sister in?

Exhausting! Not a chance in hell would I be letting this happen. I have some minor sympathy (which I feel you do too), he clearly longs for a close relationship with his family, however you can see they are absolutely abusing him, your home, hospitality, kindness and naivety.
I would initially be a tad gentle (one more conversation) with your husband, acknowledging he probably doesnt want to accept he is being used, but after that if he did not accept the truth I would be moving to my dads! Sister would not be moving in at all and overnight stays limited to when is convenient for you (if you want them at all)

This is unfortunately important.

PIL have done similar. There is also in our case some significant mental illness. SIL (mid 40s) who lives wirh PIL has spoken very inappropriately to DC and caused serious problems. DH did not stand against it in our case.

Moving into someone else's house by stealth, giving up you job and expecting them to foot all your bills without even telling them about it, is not called sharing. It's more like a mugging.

100% Agree

An equal one.

where both parties share, not just one. And both parties want to share.

family members grouping together to take advantage of another family member is obviously not sharing. Alarming you can’t see that. Are you the mil?!

Wow, I don't know you but I'm so proud of you and your husband 👏

Wonderful he stood up to them!!! And you too.

I hope she changes her mind and doesn't come.

Agree.
if on the off chance she does get a job, I think that another ‘rethink’ has occurred and the offer recalled
dh will be stronger then.
you really don’t want another woman in your kitchen- you have enough on.
especially with your dd, ds and your dh’s ongoing therapy

I’m actually starting to feel very sorry for sil.
no of course she shouldn’t move in, but sounds like they rule her life.
To smother a child to the point they have no autonomy.
it’s very sad.

They sound bonkers, but she can’t really use you all as a crutch.

I wonder if as they’re aging they’re trying to pawn her off to her brother’s care?

Stay strong @Sp3849. Do not waver!

@Sp3849

A good result for you.
I am of the same belief as the person upthread that said as soon as she moved in the In-laws would be away in the dust..

I think some posters need to read the OP's updates.

Well if the sister hadn't been daft enough to give up her job she wouldn't be needing to get back on her feet!

You are going to be paying an absolute fortune for her horse - and you know this if you are horsey. The inevitable vet's bills were the reason I eventually gave up riding and horse ownership!

You need to put an end to this, they've obviously decided she's moving in to live with you because it's more convenient for her to keep her horse there for free as well as living with you for free. You've had no say in it! You all need to grow a pair and say no. The static caravan idea was OK but still taking the piss horse-wise, but she's never leaving once she moves in.

I think when it's welcomed, agreed and reciprocal, that's fine.... but as you point put, op and her DH will be doing all the carrying!

Op make sure to check legalities with the caravan so she doesn't have a claim to land it on (tbh not sure that's a thing but worth double checking)

That was my reaction also tbh.

Good luck on getting her out when her time is up!

What works are we living in where carrying and sharing with the family is so frown upon?

I hope it all works out for you. The best outcome would be if she didn’t come at all. I worry that, if she comes, you’ll not be able to get rid of her.

Ps for context I've asked to stay over for ONE NIGHT once in my brother and sister in laws house as I was doing a training course starting early never near their house and they said no as they don't like guests on school/work nights

What a family you've married into !

@Sp3849 So DH's parents have screwed up at least two of their DC then! 😡 As others have written, please be careful how you proceed and maintain your terms and requirements of SIL. I do understand you feeling sorry for SIL, but some of us have extended the hand of kindness to someone we've felt sorry for and had it well and truly bitten off! As the saying goes, "no good deed goes unpunished".

It's really unfair how this was a gradually slippery slope into having an unpaid lodger. A word of warning my cousin did the same and her sister in law moved in for five years! Decided to retrain and do a master while living with them rent free as she could afford to! My cousin cooked dinner for her every night - her SIL basically had five years of guest level hospitality. As my cousin is a SAHM to older primary age kids I think she felt she didn't have as much say as her husband over the finances.

I think the caravan was a really fair offer and totally different to staying in the house with you. You need a spare room for your one family and friends.

I can identify with everything the O/P has posted Long story short SIL and BIL tried to foist an elderly relative off on to us, who we had little contact with for years as SIL and BIL excluded everyone and isolated relative, then got in touch years later expecting me to be a housekeeper/carer and my HB a chauffeur . they became aggressive and overbearing about it . We quickly shut all of this down even though I’m now labelled as a selfish bitch . We later found out that said relative had some potentially future serious health problems and had been sucked dry by SIL and BIL before they decided to try and dump .Good that the O/P has nipped this in the bud . Dont worry about being disliked they already do dislike you . Outsiders won’t care as it’s not happening to them and doesn't affect them so don’t worry about what others think . Good luck .