And tell me Theoretician, how much do you charge your DP to live in your property?
I love the assumption that what I think has any bearing on what happens. It's almost as though you think two people who live together should discuss who contributes what and come to an agreement. I had a similar theory, once.
My wife moved in with me. She repeatedly batted off attempts before and after moving in to discuss who would contribute what. When she got tired of me trying to start that conversation, she asked me what means I had to enforce a change to the status quo, which was her contributing nothing and making a mess of the house while staying home not working. She interpreted my being lost for words as meaning I had no sanction, and asked why she should enter into a discussion when there was no possible outcome that could improve her position. For the next several years she contributed less than fuck-all. (Nothing financially and I would have to clean up after her if I wanted the house to be as clean and tidy as it was when I lived alone.)
She did start contributing when I wanted to sell our home in London and move elsewhere, freeing up some money to retire. By then she had a job (of which she kept 100% of money for herself) and she wanted to stay in London to pursue that career. She calculated an amount that I think she mostly based on what it had previously cost her to live in a student hostel, and has paid that ever since. (Though she did ask what mortgage outgoings were, which resulted in my attempting a conversation about the irrelevance of that. You can't make someone understand something if it's in their financial interest to not understand it.)
The flat we live in, which I paid for without any help from her, would cost/bring in 30K a year rented. I now live on investment income, every 100K of mine tied up in the flat is 4K a year less income that I have. (Unfortunately no trust fund or inheritances paid for it, everything I have was generated from my own labour.)
At a rough guess I would say she currently contributes 5K a year that you could count as "rent." There is no logic to this contribution whatsoever. (To repeat: the amount was set by her according to her own bat-shit crazy logic, I had no say in it.) My original (ignored) logic that she should cover the extra cost of living in London is now irrelevant, as I no longer need/want to leave. Her (ridiculously financially illiterate) logic that the size of my mortgage outgoings were in some way relevant has apparently gone out the window, as she didn't change the amount when I paid off the mortgage in 2008. (I could have paid it off before she began contributing, but for investment and tax reasons chose not to. However I use that fact to justify my assertion that she contributed nothing to the house.)
Overall, across 18 years of marriage, and if you count the house as a joint asset, she has contributed 20% to joint costs.
Despite any appearance to the contrary I may have given, I've never needed or wanted her money. I wrongly thought that by pointing out that I was subsidising her by tens of thousands each year, I could persuade her that it was only fair she should clean up after herself. That was what I really wanted. (And before anyone says anything, no, a cleaner does not solve the problem of a messy partner.)
She wants to give up her job now, and thinks once she stops working, she should stop all financial contribution. Apparently bills are something that only you only have to pay if you have income from working. Her investment income (which is now the same as mine) can't be used to pay half the bills, but mine can be used to pay all of them. (We can each afford to pay the whole bill several times over, affordability is not the issue, fairness is. Actually it isn't: I don't give a fuck if I have to pay for everything. I'd just like to live in a clean and tidy house.)