to think DS's girlfriend is taking the piss and he needs legal advice

How exactly is she going to do that? 🤔Are you expecting OP to shapeshift into a packet of durex?

That puzzled me but presumably it's that weird English law thing of "leasehold property" where the long lease of the flat might stipulate residential use only? *

The girlfriend has no right to stay in the property even if she were to pay rent. She's a lodger- lodgers have no rights in the property they share with the owner-occupier.

The business use may well invalidate the buildings insurance unless notified to the insurer and the insurer accepts it. It probably breaches planning law as well.

*["leasehold" of residential property looks utterly bizarre from a Scots law perspective where everyone owns their flats]

Be very careful what you say to your son, he might stay with her/marry her/have children with her. Better to maintain a good relationship with him and be there to pick up the pieces if necessary. Sympathies, it is hard to watch one's adult DC making unwise choices, but they need to make their own decisions.

Given you don't wish to be identified, not easy to offer much advice as the age of your son is not mentioned. Or indeed that of his girlfriend, or much about her circumstances. If he is someone who has not found it easy in the past to form relationships, and like many considers there is a stigma in being single, you may find it hard to get him to see sense.

I agree he’s better off with her not paying rent to him - means she doesn’t have any legal right to stay in the property.

It does seem a bit off if she didn’t help out if asked when staying with you - providing your son was also helping of course, it would be a bit off if you asked her and not him. Usually family help out when staying.

Working three days a week as a MW might still be very hard work and long shifts though.

When I was young, I did say to my then boyfriend that I wasn’t going to live in a property he owned and pay rent to him. He was free to buy his own property and I would either not live with him or not pay rent but I wasn’t going to live in his flat and pay him rent. He ended up waiting til we could buy together, which was shortly before we got married in the end.

This may or may not have been sensible as we ended up divorced, but I wasn’t going to get into the situation of living with someone who was getting their mortgage paid partly by me, but took all the benefit for themselves. I could just imagine that situation going on forever.

There may also be restricted covenants on his flat that prevent a business being run. There is on my house.

He needs to check.

Presumably it's a leasehold flat that he's bought.

He’s an adult so best to mind your own business.

Sounds like this is becoming a project for you so find yourself another one.

If your son wants advice he’ll ask for it.

Your son is in a far better position, building a career and building equity, than his girlfriend. So what if she is only working 3 days a week, that will be only damaging herself in the long run, not your son. I think you should stay out of it.

You know your ds best, but normally I think it is best to accept adult dc's poor relationship choices (unless it's abusive or violent!). You can make one comment, then leave it and be welcoming and polite. Find someone discreet and loyal to complain to!

If your son owns the house, why are you mentioning anything about leases?

I think you are being unreasonable in thinking you can do anything about the situation. Your son is an adult, all you can do is be there for him if he needs you. I have run a business from my rented homes over the years and not told my landlords but it didn't involve strangers coming to the house so he really should check the terms of his mortgage to be on the safe side. Hopefully the relationship won't last too long, but we have to let our adult children make their own mistakes.

I agree with what @MistressoftheDarkSide has said above. If you do ever meet with your DS when he's not with his GF, could you have a conversation with him (I realise this sounds terribly idiotic but it might work) where you describe a situation that the son of a friend of yours is finding himself in. The friend is asking for advice and you've given yours but you are also looking for the advice of someone from a different generation as to what would be suggested to do.
It might plant a seed with your DS as to his situation. I realise that it might be idiotic but it also might work without you interfering directly into his situation.
Lots of people on MN might be against trying this but if you don't try you won't know.

advise him not to allow this, and back off. He’s an adult and won’t appreciate interference. Let him know you are there if needed.

Not quite sure how his Mum can stop that! 🤣

If she's not on the mortgage agreement then she has basically zero rights. If son wants her gone, then it's actually better for him that she pays nothing. She's the female equivalent of a cock lodger.

Yes, I think it is probably minimum wage. At first I thought it might be mid-week.

I read this earlier, I thought it was excellent, it's how to be a good parent to your adult child, you may not like it, but I think you desire to sort it was for a younger version of your son, now you need to let him work it out and pick up the pieces www.thetimes.com/article/b7a341a5-0b52-4596-ae57-7decb35ff680

She sounds like a freeloader, but I'd probably be wary of getting involved.

If he is happy with the arrangement and so is she then that is down to them. There is no point you getting involved when your opinion hasn’t been asked for, particularly since he might stay with her and go on to have DC, so it is probably in your interests not to alienate her even though you are secretly not too keen.

If she has no tenancy agreement and they aren't married I don't see that she has any rights at all.

And I would point out that running a business at the property would certainly impact on the home insurance and the new business must be declared to the insurance company - I do not know about implications regarding the property lease though, perhaps speak to the solicitor who handled the property sale.

Don't feel bad.

I read it as Midwife at first! 🙈

Doh! Of course!

I'm thinking minimum wage?