To not want to be DP’s tenant?

If OP shares this man's home and contributes to his mortgage for years or decades and then break up or he dies, she will end up homeless while he benefits from owning a house either outright or with more equity than there would have been without her contribution. This isn't fair on her.
If he doesn't care what happens to her in the event of a breakup or his death, he's being a pretty rubbish partner. Couples are supposed to care about each other's wellbeing.
There are other solutions than owning a house 50/50 together. She could own a smaller percentage than him, or instead of paying into his mortgage she could put the money into savings so at least she would have a deposit to buy or rent on her own.

Is he paying her for sex, she doesn't enjoy the sex?. Is she having sex with him for the house?

Exactly . @barhumbug can't force him to buy a house with her. The only thing you can do is to move out and pay more rent for a house share so that you can keep saving or not he able to save qt all. You would be cutting off your nose to spite your face.

Why would she be homeless?. Where was she living before she moved in with him?.she can always rent somewhere to live

He can receive approx £7500 pa tax free under the rent a room scheme.

well, you've been living rent free exactly. If you were single you'd still have to pay all bills, not 50% of them, food, white goods etc AND rent as well.

If you were to break up today, financially your DP wouldn't lose much, he'd get 25% council tax discount and his bills would be a bit lower. You'd need to pay all the bills plus housing cost. You really do benefit financially significantly from this relationship but you want even more.

You're trying to play it as lack of commitment rather than greed. Why does he need to demonstrate this to you? if he doesn't, will you leave? this means that you were with him only for money.
He really does not own you anything.

She wouldn't be a tenant and nor would anyone else. As someone living with their landlord and sharing a kitchen, she would be an "excluded occupier" under housing law and the only right she would have is to receive "reasonable" notice, which could be as little as one week (although could be a month if she were to pay him rent monthly).
The point about him paying tax on any rent she pays is a good one though (although given the thought he seems to have given to his proposal, I'd be surprised if he hasn't considered this).

Very unfair.
This reminds me of a relationship I was in. Looking back I feel like I adjusted my life to fit into his while he got to keep living life as he always had. I really think he never realized it. I brought it up years later and he said "oh whatever". 🤷🏻‍♀️ that relationship wasn't fulfilling and it kind of ran its course and was over with.
You deserve someone who makes you feel equal and involved. Not like they have something held over your head.

https://www.rightsofwomen.org.uk/get-advice/family-law-information/a-guide-to-financial-arrangements-after-marriage-breakdown/

https://www.rightsofwomen.org.uk/wp-content/uploads/2023/12/row--legal-guide-marriage-home-rights-final.pdf

You may want to read these guides - your DH may not be on the deeds, but as your husband, he can register his "home rights" at the matrimonial home. This can impact your ability to sell in the case of a split.

After a long marriage, the house will very likely be taken into consideration when splitting marital assets, based on your respective incomes, quality of life, and responsibility to children (or not). Marriage supercedes any previous agreements, and if there is an existing deed of trust it will be taken as an indication of intent but not necessarily as still legally binding.

EDIT: Just seen your update that you are not in England/Wales - however I am leaving the post up for info for anyone who is married but not named on the deeds of the matrimonial home.

Not correct. I am not in England. Where we live, any property in divorce is kept by the owner. Also, inheritances are not part of any settlements. So, the opposite to England in both regards.

My friend is going through a divorce right now. Her husband has 5 properties and is walking away with those intact. She has no claim. They have been married for almost 20 years. Even the home they lived in was his. Thankfully, she has been able to buy that from him and stay in it. Luckily she inherited a lot of money last year and he can't touch that.

Anyway, back to Op - if she wants a property she can save a deposit and buy one, and rent it out if she's living with her partner. She is living rent free right now - not many people are that lucky - which should mean she has a good opportunity to save.

And I do think that any woman posting here about whether to add a boyfriend to her property deeds, would be told NO.

Then she could go and pay rent somewhere else then

Fair point!

He's treating her as a bank. She's helping subsidise his living costs while he builds up equity in a house and she gets nothing.

OP, he really wants everything his own way.
It would really suit him to have a tenant that will have sex with him as he builds equity in this new house.
A great arrangement for him.

For you it will be a dreadful arrangement.
You deserve better.
You need to focus fully on saving everything you can to get a tiny property for yourself.

I wouldn't waste my future on a man that is so utterly focused on himself and his security.

Don't be his housekeeper tenant that has sex with him.

You deserve so much better.
Let him get a tenant and pay tax on it.

Have you mentioned him paying tax?....bet he'd love that.
Have you spoken out about renter rights etc.?

And her a free house keeper, sex worker?

I understand he has worked very hard for his home and I wouldn’t want to take any of that away from him

Trouble is, this is what so many say - the ex who burned him may well have said it too - but once on the deeds it can become "Well, my small contribution's JUST the same proportion of what I could afford", "He only got that raise/promotion because I was doing the housework" and so on

As for "if I was on a mortgage with DP I’d only be paying the £500 mortgage plus bills so the extra £800 I’d save from not having to pay rent/mortgage on a second place would be my savings. If I had to pay that out to have my own place I’d have nothing left" he's probably worked that out too and may even have decided there's rather a lot of focus on his money

How is it fair when he’s putting in two thirds of the cash and half of the mortgage

This plus ask him what happens to his house if he were to die?

How much rent can he reasonably expect from a lodger who shares a room with him? Its nothing like renting an actual room to someone. I doubt the little bit extra he would stand to gain from this would enable his house purchasing hike up the property ladder.

For this to be in anyway fair, it needs to be a joint enterprise where you you would own the house proportionate to what you had put in and how much of the mortgage you are sharing. If he is not willing to take this step then I would not be engaging with this plan at all. Keep putting money aside so that you can comfortably leave if/when you need, as that is clearly his perspective.

I get that you think by protecting his deposit it's a good thing. If you buy a £300k house you’d protect his deposit of £290k and you'd put in £10k deposit

why on earth though @barhumbug do you think you’d be entitled to half the equity going forward for paying a few hundred quid mortgage when you've just been paying contributions to running costs for the last 4 years to pay off your debts

Isn't that what the OP was suggesting?

Yes even squatters rights kick in before 17 years! ?

Yeah, as a pp said, it's not YOUR home. You are married. It's 50% his.

. 😂

This man has shown that he only cares about his own financial interests. He’s entitled to do that, but he’s leaving the OP in a very vulnerable financial position.

I wouldn’t blame her if she started putting her own interests first. Which could mean saving up until she has enough for a deposit, then moving out. Not because “a man is a bank”, but because it’s far easier to save when you’re living with someone and sharing the living costs.