tl;dr: partner owns his property outright and wants me to pay him rent on top of bills etc.
I have recently moved in with my partner of 3 years. He owns his (2 bed) property outright: he bought it with money from a family trust set up for him when he was born. He rents out one bedroom to his friend for £700 / month. We share the other bedroom. He wants me to pay him £350 / month on top of all bills which are split equally three-ways. We also split the cost of any house repairs that need doing.
He says the arrangement will make us both richer -- as I will be paying less than market rent for a similar room.
When we first spoke about finances, before I moved in, he said that the money I saved in rent could be put towards making our lives 'bigger'. When discussing this recently, he said that this was still true, that the money I pay him can go towards his masters course fees for example, and that this will benefit us both long-term.
The amount is small, but I'm not sure how I feel about it in principle. Because he pays no rent or mortgage, I can't see why I should pay him rent. On the other hand I am benefitting hugely - the flat is lovely, we are making a home together, and I am able to save more money than if I were renting on the private market. On the other other hand I am very much sharing his room, and there is not much space in the flat for my things (they are currently in boxes in cupboards / storage)
I also end up doing most of the housework and I worry that if I am giving him money on top of that and on top of bills etc I will become resentful. I'm also not sure what his motivations are for asking me to give him money, since he doesn't really need it.
What do you think?