AIBU for not wanting to pay rent?

That sounds like a great approach @freebirdblue good luck with the viewings

Good decision, I hope goes well for you - please keep your flat hunting to yourself. Don't them catch you at wobbly moment and talk you out of it.

Please update us later

150 or 100 seems fine rent wise but only while you’re living there.

I guess the takeaways are a swap for her cooking.

personally I’d get out asap, You need to live 20 or 30 minutes away and aim to see her family weekly. Maybe you could babysit while they have a weekly date night.

Well done. Crossing and hoping!

Best of luck with it . Hope you get something.

I think that yes you should plan to move out.
re: the £100 I would say to DSis and BIL, if I have to pay that to you, I am going to have to move back in completely. Please can you let BILs parents know I will be leaving their home when I start paying you, as I can’t afford both. They will have to find someone else. And they need to pay me the vet’s fees back ASAP.

Nope-it £5200 as she pays £100/week

There is no opportunity cost to the sister of OP not paying rent for two months because DSis wouldn’t be doing anything to generate income from the room anyway. They have a friend coming to stay on and off which is a clear indication that they are not looking to commercialise the spare room.
Therefore they are not losing out on an opportunity.

But which came first - the chicken or the egg? Or in this case, the OP temporarily moving out, or the friend needing occasional accommodation? It doesn’t matter if OP’s sister intends to capitalise on having a spare room - the OP’s request to have it held for two months impacts the option to do this. How do you know she didn’t want to get a new lodger instead, but because OP plans on coming back, she’s decided to let her friend use the room occasionally instead?

OP can’t be expected to pay £800-900 because in some alternate reality they would have rented the room to another tenant.

Well actually, yes she could. All this “alternate reality” business is nonsense. If this was Mrs Wallace at No. 24 letting her room to the OP instead of OP’s sister, and OP wanted to disappear for two months, but still have the room available once she returned (and to leave all her stuff behind), everyone would be saying that of course she should pay.

However, the big difference here is that OP’s sister wants use of the spare room as a guest room in the meantime. Because of this, as I’ve now stated many times, OP should pay an agreed retainer, not full rent.

I’m not sure you fully grasp what an opportunity cost is, but you’re pretty close.

I think it’s you who hasn’t quite understood, given your quite simplistic approach, but thanks.

You need to reply: you will have to tell Bil I needs to drop housesitting, I can’t afford it and all this extra. I have messaged his parents to say they will have to pay remotely at the vet before the treatment, I can’t pay it for them.

Move out asap asap asap asap

There is no opportunity cost to the sister of OP not paying rent for two months because DSis wouldn’t be doing anything to generate income from the room anyway. They have a friend coming to stay on and off which is a clear indication that they are not looking to commercialise the spare room.

Therefore they are not losing out on an opportunity.

If there was an opportunity cost to OP not paying rent, I would have said to pay it.

OP can’t be expected to pay £800-900 because in some alternate reality they would have rented the room to another tenant.

I’m not sure you fully grasp what an opportunity cost is, but you’re pretty close.

OP - it's actually heartbreaking reading your posts. You're being taken advantage of, horribly.

Were you not related this would be considered exploitation, right down to selling you a vehicle that's constantly needing work done on it.

This is an incredibly sad situation for you but you HAVE to get out of.

You keep missing the point. It doesn’t matter whether OP thinks her sister will get a lodger, or even if the sister has no intention of doing so. It’s about opportunity cost.

35k is peanuts, it doesn't go far at all once tax, student loan and pension come out, but since they are massively underemployed it will sound like a lot to them.

Yes. Plus, on a low income with two DC, they'll be getting benefits. I'm out of touch with current levels and we don't know how old the kids are, but I bet they don't talk about the extra money as much as they talk about OP's.

Get out fast and never agree to do anything for her partners family again. Don't pay for the bloody vet bills either, that's ridiculous. Put your foot down now and refuse to pay any more because it's highly likely they have no intention of paying you back.

35k is peanuts, it doesn't go far at all once tax, student loan and pension come out, but since they are massively underemployed it will sound like a lot to them.

150 per week is reasonable if it includes meals but the childcare and dogsitting is actual work. That needs to be factored in.

The whole thing is messy and bound to cause trouble, better to move out and stay out of the boyfriends parents dog/house care arrangements in future because honestly, it reads like they've taken you for a mug there.

I wondered why an energetic dog like a collie wasn’t going running! It’s terribly outing when the dog is too familiar with the OW 😜

She wouldn’t be getting another lodger. This isn’t a lodger situation. This is OP’s sister doing her a “favour”.

My son has a useful word for this ‘volun-told’ I.e. where you ‘volunteer’ for something that comes with a large side order of guilt/obligation. School are good at using this to get him to do extra things (parents evening, helping younger students etc) but at least at 18 he can identify when he’s been put under slightly unreasonable pressure!
I think OP would really benefit from some assertiveness training.

Could you suggest to BIL that he asks his parents to make up the £50 they're losing with you at theirs (if you just pay them £50 that is)?

What a bizarre situation! And how complicated!
Your sister sounds very conflicted about who is helping who here, as well as who needs what. The whole thing sounds quite bonkers to me as an outsider; why should you pay your sister to put you up when you're not there, and why did she let her partner's parents borrow you to use you as a house sitter in the first place, when she needed your rent?
I'd be inclined to move into your own place as soon as you can, because this situation may get even more weird.

2-3hr runs. He's having an affair, isn't he 🤔

Also it is outrageous BIL goes for 2-3h runs and leaves you to do childcare and walk the dog!

I'm really sorry your sister exploits you and your concern for her, @freebirdblue. It's a lot to take on board at your young age, when you should be enjoying your freedom and exploring possibilities.

As you've noticed yourself, your BIL's parents may well fail to pay you back for the vet. Can he pay their medical fees? Or at the very least, take it off the £50 a week (not £100 or £150!) they want to charge you while you're not living with them.

Stop buying your sister treats and subbing her kids' childhoods. Stick to birthdays and Christmas, and don't go overboard on those either.

Well done for finding out the costs of alternative accommodations. A room in a shared house will cost roughly the same as staying at your sister's and, without feeling obliged to pay for their takeaways, coffees and lunches, you'll be better off!

Your sister's going to take it badly but that was going to happen, however this arrangement ended. I hope your workplace support can find you a slot to help strengthen you. Good luck!

OP, I hope that you gather up the courage to move out and save both money and heartache.

Exactly according to OP they wouldn’t have a lodger in there if she wasn’t there so they’re not keeping it open especially when they’ll be using it as a guest room.

She assumes they won’t have a lodger if she leaves. But you’re missing the point. There doesn’t have to be a lodger lined up, or even any intention to have one. What OP would be paying for is the guarantee she will get the room back. It’s all very well saying “Oh, she won’t get another lodger” - we’re talking about the option to have one.

The sister using it as a guest room is a separate issue. I would not be happy about it personally, but it is absolutely not the same as a sub-let or replacing the OP on a long-term basis.