It seems we may just have different morals that no amount of back and forth will rectify. I apologise for sounding like a broken record but I'm responding to several people with similar arguments and memmy ain't as good as keeping track of context as Apollo was.

I actually live this scenario and have an equity agreement that splits the sale proceeds proportional to what each person put in. I find the idea of land lording over a partner to be disgusting.

If you want your girlfriend to live with you then what's the alternative? She move out and buy a second house? If you want her to live with you then she shouldn't have to put her financials on hold to do so.

But I agree that it's case by case. In several other places I've said that I don't expect their recent girlfriend to get a cut of their boyfriend's house just because her lease expired when they started dating. The longer she lives there though, the more I think the conversation should be had.

I really don't have a defining line. It's very grey for me. I wouldn't expect someone to take out a HELOC to pay out equity for their girlfriend that moved into a house, that he already owned, for six months. But on the other extreme, a couple that has been living together for five years feels like she should get something. Especially if she helped with the down payment like my GF did.

Where the line between these two extremes is? I don't really have a catch all answer. It'd have to be case by case.